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Encyclopedia – For the user of petroleum products

ExxonMobil Corporation – Copyright 1993-2019


abrasion - the process of scraping or wearing away.

abrasive wear - the loss of material due to hard particles or hard protuberances that are forced against and move along a solid surface.

absolute humidity - see humidity.

absolute pressure - see pressure; is equal to gauge pressure plus atmospheric pressure.

absolute scale - see temperature scales.


absolute viscosity - the ratio of shear stress to shear rate. It is a fluid's internal resistance to flow. The common unit of absolute viscosity is the poise (see viscosity). Absolute viscosity divided by the fluid's density equals kinematic viscosity.


absorbent filter - refers to a process by which a liquid or gas is taking into an absorbent material and dissolved uniformly inside of it. 

absorber oil - oil used to selectively absorb heavier hydrocarbon components from a gas mixture. Also called wash oil or scrubber oil.


absorption - the assimilation of one material into another; in petroleum refining, the use of an absorptive liquid to selectively remove components from a process stream.


accumulator - an apparatus for storing energy or power, ex. Hydraulic fluid under pressure. 

ACEA - European Automobile Manufacturers Association. Mission is to define and advocate the common interests, policies, and positions of the European automobile industry.

acetylene - highly flammable hydrocarbon gas (C2H2), used in welding and cutting, and in plastics manufacture. Also, a term for a series of unsaturated aliphatic hydrocarbons, each containing at least one triple carbon bond, the simplest member of the series being acetylene. The triple carbon bond makes acetylenes highly reactive. see unsaturated hydrocar­bon.


acids - hydrogen-containing compound that reacts with metals to form salts, and with metallic oxides and bases to form a salt and water. The strength of an acid depends on the extent to which its molecules ionize, or dissociate, in water, and on the resulting concentration of hydrogen ions in solution. Petroleum hydrocarbons, in the presence of oxygen and heat, can oxidize to form weak acids, which attack metals. see corrosion, oxidation.


acidity - the level of acid in substances.

acidizing - treatment of underground oil-bearing formations with acid to increase production. Hydrochloric or other acid is injected into the formation and held there under pressure until it etches the rock, thereby enlarging the pore spaces and passages through which the oil flows. The acid is then pumped out and the well is swabbed and put back into production.

acid number - see neutralization number.


acid treating - refining process for improving the color, odor, and other properties of white oils or lube stocks, whereby the unfinished product is contacted with sulfuric acid to remove the less stable hydrocarbon molecules.

acid wash color - an indication of the presence of olefins and polar compounds in petroleum solvents. A sample of solvent is mixed with sulfuric acid and let stand until formation of an acid layer, the color of which is compared against color standards.

acrylic resin - any of a group-of thermoplastic resins formed from the polymerization (see polymer) of acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile. It is used in the manufacture of lightweight, weather-resistant, exceptionally clear plastics.

actuator - a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve

acute effect - toxic effect in mammals and aquatic life that rapidly follows exposure to a toxic substance. An acute effect is usually evident after a single oral in-take, a single contact with the skin or eyes, or a single exposure to contaminated air lasting any period up to eight hours. Also known as acute toxicity. see chronic effect health hazard.


acute toxicity - see acute effect.


additive - chemical substance added to a petroleum product to impart or improve certain properties. Common petroleum product additives are anti-foam agent, anti-icing additive, anti-wear additive. Also, corrosion inhibi­tor, demulsifier, detergent, dispersant, emulsifier, EP additive, oiliness agent, oxidation inhibitor. And pour point depressant, rust inhibitor, tackiness agent, viscosity index improver.


adhesion - the tendency of dissimilar particles or surfaces to cling to one another.

adhesive wear - adhesive wear is caused by relative motion, "direct contact" and plastic deformation which create debris and material transfer from one surface to another.

adiabatic compression - compression of a gas without extraction of heat, resulting in increased temperature. The temperature developed in compression of a gas is an important factor in lubrication since oil deteriorates more rapidly at elevated temperatures. Oxidation inhibitors help prevent rapid lubricant breakdown under these conditions.

adjuvant - material added to a pesticide formulation that enhances the performance of the active ingredient. Petroleum oils are commonly used as adjuvants. An adjuvant can improve pesticide effectiveness in a variety of ways. For example, by reducing surface tension. This permits finer droplet size and better surface coverage. While reducing volatility, which minimizes evaporation to control spray drift and provide adequate surface residence time. This lowers water solubility to resist rain wash-off and weathering. It also modifies plant or insect surfaces to improve pesticide uptake. see agricultural oil.


adsorbent filter - is comprised of media that captures materials on the element surface.

adsorption - adhesion of the molecules of gases, liquids, or dissolved substances to a solid surface, resulting in relatively high concentration of the molecules at the place of contact, e.g., the plating out of an anti-wear­ additive on metal surfaces. Also, any refining process in which a gas or a liquid is contacted with a solid, causing some compounds of the gas or liquid to adhere to the solid, e.g., contacting of lube oils with activated clay to improve color. see clay filtration.


aeration - the process in which air is circulated through, mixed with or dissolved in a liquid or substance.

aerosol - a highly dispersed suspension of fine solid or liquid particles in a gas. Petroleum solvents are commonly used either as carriers or as vapor pressure depressants in packaged aerosol specialty products. Petro­leum products are also applied in aerosol form in agricultural oil applications and oil mist lubrication.


after-cooling - the process of cooling compressed gases under constant pressure after the final stage of compression. see inter-cooling.


after-running - the continued running of a spark- ignited engine after the ignition is turned off; also known as dieseling. There are two basic causes of after-running: surface ignition and compression ignition. In surface ignition, the surfaces of the combustion chamber remain hot enough to provide a source of ignition after the spark ignition is terminated. In compression ignition, the conditions of temperature, pressure, fuel com­ position, and engine idle speed allow ignition to continue. see compres­sion ignition.


age hardening - increase in the consistency of a lubricating grease with storage time.

agglomeration - a mass or collection of deposits.

AGMA - American Gear Manufacturers Association, which as one of its activities establishes and promotes standards for gears and lubricants.


AGMA lubricant numbers - AGMA specification covering gear lubricants. The viscosity ranges of the AGMA numbers (or grades) conform to the International Standards Organization (ISO) viscosity classification system.

agricultural oil - petroleum product either applied directly on plants as a pesticide or used as an adjuvant to enhance the effectiveness of a pesticide. A good agricultural oil should have low volatility for longer adherence to leaf surfaces, low surface tension for better surface coverage and easier atomization, and low water solubility to resist rain wash-off. There are two basic types of agricultural oil: orchard spray oil and crop oil. The former should have low phytotoxicity (harmfulness to plants); this is accomplished by controlling molecular weight within optimal limits and by maximizing unsulfonated residue content. A crop oil is lower in quality and commonly used as an adjuvant in herbicide spray formulations.

air blowing - see air sparging.


air breather - filters air that is drawn into equipment through a media designed to stop particulate and sometimes moisture.

air entrainment - presence in an oil of minute bubbles in colloidal-like suspension, giving the liquid a cloudy or hazy appearance. The bubbles are difficult to expel, as distinct from foam, which consists of relatively large bubbles that tend to rise and eventually escape from the oil. In a lubricating oil, entrained air can disrupt the lubricating film and cause excessive surface wear. Because entrained air is compressible, it can cause erratic and inefficient operation of hydraulic systems. A common cause of air entrainment is excessive use of silicone in treating foaming problems. ASTM D3427 measures the ability of an oil to separate entrained air. see colloid, emulsion.


air-line lubricator - Often found in compressed air systems to regulate pressure, filter the air and to provide the proper amount of lubricant to air driven tools.

air / oil hydraulics - Often used in low power circuits where air cylinders provide thrust while oil controls the speed and stopping. The air power cylinders are often self-contained with built in oil reservoirs.

air / oil separator - a mechanical device that removes air from oil.

air release - The ability of a lubricant to give up air that has been forced into solution.

air sparging - a mixing process, commonly used in lube blending plants, that employs compressed air as the mixer. Air is injected into the bottom of the tank through multiple ports, and its upward movement through the liquid provides the mixing. If dry air is used, the process can remove entrained water from the lubricant. Nitrogen or an inert gas is sometimes used in place of air in this process. Sparging is not done with lubricants that contain volatile components (such as solvents) or that are susceptible to color change when heated and air blown.

AIST - an organization focused on promoting the international iron and steel industry through networking and education.

alcohol - any of a class of chemical compounds containing a hydroxyl (OH) group with the general formula of CnH2n+1OH.

aldehyde - any of a class of highly reactive organic compounds contain­ing the CHO radical; can be formed during petroleum product oxidation and can contribute to deposit formation.

aliphatic hydrocarbon hydrocarbon in which the carbon atoms are joined in open chains, rather than rings. see hydrocarbon, normal paraf­fin.


alkali - a hydroxide or carbonate of an alkali metal (e.g., lithium, sodium, potassium, etc.), the aqueous solution of which is characteristically basic in chemic al reactions. The term may be extended to apply to hydroxides and carbonates of barium, calcium, magnesium, and the ammonium ion. see base.


alkane hydrocarbon having the general formula CnH2n+2; also called a paraffin.


alkyl - any of a series of monovalent radicals having the general formula CnH2n+1, derived from aliphatic hydrocarbons by the removal of a hydrogen atom; for example, CH, (methyl radical, from methane).


alkylate - product of an alkylation process.

alkylated aromatic -benzene-derived synthetic lubricant base. This compound showcases good hydrolytic stability, which resists chemical reactions with water. Additionally, it possesses good compatibility with mineral oils. Used in turbines, compressors, jet engines, and hydraulic power steering.

alkylation - in refining, the chemical reaction of a low-molecular­ weight olefin with an isoparaffin to form a liquid product, alkylate, that has a high-octane number and is used to improve the antiknock properties of gasoline. The reaction takes place in the presence of a strong acid catalyst, and at controlled temperature and pressure. Alkylation less commonly describes certain other reactions, such as that of an olefin with an aromatic hydrocarbon.

all-loss lubrication - A total-loss oiling system whereby oil is introduced into the application and then consumed; not returned to the reservoir. Examples include a mist system for bearings or a cylinder lube for a reciprocating compressor.

allotrope - a different molecular form of the same element, e.g., oxygen O2, and ozone O3.

aluminum rolling oil - petroleum liquid sprayed onto the work rolls and backup rolls of an operating aluminum rolling mill. Its primary purpose is to cool the rolls and provide the necessary lubricity to promote formation of a foil, or sheet, that is of uniform thickness and does not tear or adhere to the work rolls. A good aluminum rolling oil should possess several properties. It needs to have effective cooling capability and suitable viscosity. The oil should resist viscosity change under pressure. It also requires good oxidation stability and demonstrates a high flash point. The oil should exhibit low vapor pressure and a narrow distillation range. It needs to comply with FDA standards and have appropriate taste properties. Lastly, desirable features include low odor and a light color. See rolling oil.


ambient - pertaining to any localized conditions, such as temperature, humidity, or atmospheric pressure, that may affect the operating characteristics of equipment or the performance of a petroleum product, e.g., a high ambient temperature may cause gasoline vapor-lock in an automobile engine.

American Gear Manufacturers Association - see AGMA.


American National Standards Institute - see ANSI.


American Petroleum Institute - see API.


American Society for Testing and Materials – see ASTM.


amine - are compounds and functional groups that contain a basic nitrogen atom. Amines are formally derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by an alkyl or aryl group.


ampere - a unit of electric current equal to a flow of one coulomb per second. A base unit for electric current.


amphoteric - having the capacity to behave as either an acid or base; e.g., aluminum hydroxide, Al(OH)3, which neutralizes acids to form aluminum salts and reacts with strong bases to form aluminates.

analytical ferrography - Works through magnetic separation of contaminant particles in which a sample of a machine's oil is taken and diluted, then run across a glass slide. The slide is then placed on a magnetic cylinder that attracts the contaminants. Non-magnetic contaminants remain distributed across the slide from the wash. These contaminants are then washed, to remove excess oil, heated to 600°F for two minutes, and the slide is analyzed under a microscope.

anesthetic effect - the loss of sensation with or without the loss of consciousness. It can be caused by the inhalation of volatile hydrocarbons. See volatility.


angular velocity - Is the rate at which an object rotates around a chosen center point.

anhydrous - devoid of water.

aniline point -the lowest temperature at which a certain amount of aniline is soluble in a particular amount of a petroleum product. The lower the aniline point, the higher its solvency. Paraffinic hydrocarbons have higher aniline points than aromatic types.

anionic emulsified asphalt - see emulsified anionic asphalt.


ANSI (American National Standards Institute).  Organization of industrial firms, trade associations, technic al societies, consumer organizations, and government agencies. It's intended to establish definitions, terminologies, and symbols. Also, improve methods of rating, testing, and analysis. It coordinates national safety, engineering, and industrial standards. In addition to representing U.S. interests in international standards work.

anti-foam agent - one of two types of additives used to reduce foaming in petroleum products: silicone oil to break up large surface bubbles, and various kinds of polymers that decrease the amount of small bubbles entrained in the oils. See foaming.


anti-friction bearing - any rolling contact bearing, as contrasted with a sliding, or plain, bearing. Anti-friction bearings have key advantages. They effectively reduce friction and can operate for extended periods with minimal grease or oil. They are ideal when lubrication frequency is low, such as in automobile wheels, or where lubricant supply is limited.

anti-icing additive - substance added to gasoline to prevent ice forma­tion on the throttle plate of a carburetor. Anti-icing additives are of two types: those that lower the freezing point of water, and those that alter the growth of ice crystals so that they remain small enough to be carried away in the air stream. See carburetor icing.


anti-knock - resistance of a gasoline to detonation in a combustion chamber. See antiknock index, knock, octane number.


anti-knock compounds - substances which raise the antiknock quality of a gasoline, as expressed by octane number. Historically, tetraethyl lead (see lead alkyl) has been the most common antiknock compound, but its use is being phased out under Environmental Protection Agency (EPA) regulations. Coming into increasing use as octane boosters are toluene and oxygenated organic type substances such as methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME). See knock.


anti-knock index - the average of the Research Octane Number and Motor Octane Number; a measure of the octane quality of a gasoline. See knock, octane number.


anti-locking brakes - is a non-skid braking system used on vehicles, which operates by preventing the wheels from locking up during braking, thereby maintaining tractive contact with the road surface.

antioxidant - see oxidation inhibitor.


anti-seize compound - grease- like substance containing graphite or metallic solids, which is applied to threaded joints, particularly those subjected to high temperatures, to facilitate separation when required. See thread compound.


anti-wear additive additive in a lubricant that reduces friction and excessive wear. See boundary lubrication.


anti-whip bearing - a bearing designed to specifically suppress vibration in lightly loaded high speed shafts. Most often found in turbines they are typically three lobe or tilt pad type plain bearings.

API (American Petroleum Institute) - a trade association. It consists of petroleum producers, refiners, marketers, and transporters. Its purpose is to advance the petroleum industry. They do this by conducting research and disseminating information. They also foster cooperation between government and the industry on mutual matters. One API technical activity includes the establishment of API Engine Service Categories for gasoline and diesel engine oil quality.

API gravity - see specific gravity.


apparent viscosity - viscosity of a fluid that holds only for the shear rate (and temperature) at which the viscosity is determined. See shear stress, Brookfield viscosity.


arc of approach - a gear term. The distance traveled by a point on either pitch circle of the two wheels from the point of engagement to the pitch.

aromatic - unsaturated hydrocarbon identified by one or more benzene rings or by chemical behavior similar to benzene. The benzene ring is characterized by three double bonds alternating with single bonds between carbon atoms (compare with olefins). Because of these multiple bonds, aromatics are usually more reactive and have higher solvency than paraffins and naphthene. Aromatics readily undergo electrophilic substitution; that is, they react to add other active molecular groups, such as nitrates, sulfonates, etc. Aromatics are used extensively as petrochemical building blocks in the manufacture of pharmaceuticals, dyes, plastics, and many other chemicals.

aryl - any organic group derived from an aromatic hydrocarbon by the removal of a hydrogen atom, for example C6H5- (phenyl radical, from benzene).


ash content - noncombustible residue of a lubricating oil or fuel. Lubricating oil detergent additives contain metallic deriva­tives, such as barium, calcium, and magnesium sulfonates, that are common sources of ash. Ash deposits can impair engine efficiency and power. See detergent.


ashless dispersant - see dispersant.


askarel - generic term for a group of synthetic, fire-resistant, chlorinated aromatic hydrocarbons used as electrical insulating liquids. Gases produced in an askarel by arcing conditions consist predominantly of non-combustible hydrogen chloride, with lesser amounts of combustible gases. Manufacture of askarels has been discontinued in the U.S. because of their toxicity. See PCB.


ASM International - American Metal Society International. An organization which connects materials professionals with the resources available to solve problems, improve materials performance, and support professional development.

ASME - American Society of Mechanical Engineers. An organization that enables collaboration, knowledge sharing, career enrichment, and skills development across all engineering disciplines, toward a goal of helping the global engineering community develop solutions to benefit livelihoods.

asperities - microscopic projections on metal surfaces resulting from normal surface-finishing processes. Interference between opposing as­perities in sliding or rolling applications is a source of friction and can lead to metal welding and scoring. Ideally, the lubricating film between two moving surfaces should be thicker than the combined height of the opposing asperities. See boundary lubrication, EP additive.

asphalt - brown-to-black, bituminous material (see bitumen) of high molecular weight, occurring naturally or as a residue from the distillation of crude oil; used as a bonding agent in road building, and in numerous industrial applications, including the manufacture of roofing. Blown, or oxidized asphalt is produced by blowing air through asphalt at high temperatures, producing a tougher, more durable asphalt. See also asphalt cement, asphaltenes, emulsified anionic asphalt, emulsified cationic asphalt, emulsion flux asphalt, penetration grading (asphalt ), polymer­ modified asphalt, reclaimed asphalt pavement, recycling of asphalt paving, viscosity (asphalt ), viscosity grading (asphalt).


asphalt cement (AC) - asphalt refined to meet specifications for paving and special purposes. Specifications are established by ASTM and the American Association of State Highway Transportation Officials (AASHTO).

asphaltenes - high- molecular weight hydrocarbon components of asphalt and heavy residual stocks (see bottoms) that are not soluble in n­-pentane as described in ASTM D3279 Standard Test for n-Heptane Insolubles. This method is applicable to all solid and semi-solid petroleum asphalts containing little or no mineral matter, to gas oils, to heavy fuel oils, and to crude petroleum that has been topped to a cut-point of 650°F (343°C) or higher.

asphalt grading - see penetration grading (asphalt), viscosity grading (asphalt).


asphaltic - containing significant amounts of asphaltenes.


Asphalt Institute - an international, non-profit association sponsored by members of the petroleum asphalt industry that serves both users and producers of asphaltic materials through programs of engineering service, research, and education.

asphalt paving - road paving made of materials such as aggregate (crushed stone, pebbles, shells, etc.) held together with a binder of asphalt cement.


asphalt recycling - see recycling of asphalt paving.

aspiration - drawing of air at atmospheric pressure into a combustion chamber as opposed to supercharging or turbocharging.

ASTM (American Society for Testing and Materials) - organization devoted to "the promotion of knowledge of the materials of engineering, and the standardization of specifications and methods of testing." A preponderance of the data used to describe, identify, or specify petroleum products is determined in accordance with ASTM test methods.

ASTM scale (D 1500) - see color scale.


ATF - see automatic transmission fluid.


atmosphere - unit of pressure equal to 101.3 kilopascals (kPa), or 14.7 pounds per square inch (psi), or 760 mm (29.9 in) of mercury, standard atmospheric pressure at sea level.

atmospheric pollutants - see pollutants.


atmospheric pressure - see pressure.


atomic absorption spectroscopy - a spectra-analytical procedure for the quantitative determination of chemical elements using the absorption of light by free atoms in a gaseous state.

atomization - the reduction of a liquid into fine particles or spray. Atomization of a fuel is necessary for efficient combustion. Atomization is accomplished by the carburetor or the fuel injection system in internal combustion engines, and by special steam or air atomizers in furnaces and boilers. Other types of petroleum products are atomized in oil mist lubrication and agricultural oil applications.

Austempering - see quenching.


autoignition temperature - the lowest temperature at which a flammable gas or vaporized liquid will ignite in the absence of a spark or flame, as determined by test method ASTMD 2155; not to be confused with flash point or fire point, which is typically lower. Autoignition temperature is a critical factor in heat transfer oils and transformer oils, and in solvents used in high-temperature applications.

automatic transmission - is a type of motor vehicle transmission that can self-shift change gear ratios as the vehicle moves under power.

automatic transmission fluid (ATF) - fluid for automatic transmissions in motor vehicles. Automatic transmission fluids must have a suitable coefficient of friction, good low-temperature viscosity, and anti­-wear properties. Other necessary properties are high oxidation stability, anti-corrosion, anti-foaming, and compatibility with synthetic rubber seals. See corrosion, foaming.


automotive emissions - see emissions (automotive).


aviation gasoline (avgas) - high-quality gasoline type. It's produced under strict controls to meet demanding performance and safety standards required by piston-type aircraft engines. Volatility of aviation gasoline is closely controlled since, in most aircraft engines, excessive volatility can lead to vapor lock. Aviation gasolines generally have lower vapor pressure and a narrower distillation range than automotive gasolines (see distillation test). Aviation gasolines are formulated to resist chemical degradation and to prevent fuel system corrosion. There are two basic grades of aviation gasolines (based on their antiknock value): 80 (80 lean/87 rich) and 100 (100 lean/130 rich). Aviation gasoline has different properties than turbo fuel, which fuels gas-turbine-powered aircraft. See lean and rich octane number.


axial flow - movement in the direction of the axis. See compressor, pump.


axially loaded bearing - typically an anti-friction bearing where part or all the load is parallel to the shaft journal or center of rotation.

azeotrope - liquid mixture of two or more components that boils at a temperature either higher or lower than the boiling point of any of the individual components. In refining, if the components of a solution are very close in boiling point and cannot be separated by conventional distillation, a substance can be added that forms an azeotrope with one component, modifying its boiling point and making it separable by distillation.


babbitt - is an alloy used for the bearing surface in a plain bearing.

backlash - the amount of clearance between mated gear teeth.

back pressure - Refers to physical force opposed to the desired flow of gases in confined places such as an exhaust pipe. 

bacteria - are prokaryotes, which consist of a single cell with a simple internal structure. They are microscopic single-celled organisms that thrive in diverse environments like water soluble cutting oil.

bactericide - additive included in the formulations of water-mixed cutting fluids to inhibit the growth of bacteria promoted by the presence of water, thus preventing the unpleasant odors that can result from bacterial action.

baffle - in a hydraulic reservoir, a vertical plate separating the return oil from the oil near the pump inlet. Used to reduce the effects of turbulent oil flow and promote contamination drop out of the return oil.

ball bearing - a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce friction and support loads.


ball joint - in an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles. Allows pivot between the wheels and the suspension in the front of a vehicle.


barium - is a chemical element with the symbol Ba and the atomic number of 56. It is often used as a detergent in engine oil.


barium complex - a thickener used in grease with excellent resistance to water washout.

barrel - standard unit of measurement m the petroleum industry, equivalent to 42 standard U.S. gallons.

base - any of a broad class of compounds, including alkalis, that react with acids to form salts, plus water. Also known as hydroxides. Hydroxides ionize in solution to form hydroxyl ions (OH-), the higher the concentration of these ions, the stronger the base. Bases are used extensively in petroleum refining in caustic washing of process streams to remove acidic impurities and are components in certain additives that neutralize weak acids formed during oxidation.


base circle - the circle of an involute gear wheel from which the involute forming the outline of the tooth face is generated.

base coat - see launching lubricant.


base number - see neutralization number.


base stock - a primary refined petroleum fraction, usually a lube oil, into which additives and other oils are blended to produce finished products. See distillation.


basin - trough-like geological area, the former bed of an ancient sea. Because basins consist of sedimentary rock and have contours that provide traps for petroleum, they are considered good prospects for exploration.

batch - quantity of product resulting from one blending or other processing operation. See blend.


batch blending - in petroleum product manufacture, mixing of two or more components in a container, such as a tank or kettle, to achieve desired physical or chemical properties. See batch, blend, line blending.


batch purification - refers to a filtration process where oil contaminants such as insolubles and water are removed. Upon completion the oil is returned or placed into service. 


beam strength - capability of a gear tooth to withstand repeated bending stress under load.


bearing - basic machine component designed to reduce friction between moving parts and to support moving loads. There are two main types of bearings: (1) rolling contact bearings (also called anti-friction hearings) commonly ball or roller, and (2) sliding (plain) bearings, either plain journal (a metal jacket fully or partially enclosing a rotating inner shaft) or pad-type bear­ings, for linear motion. Roll­ing contact bearings are more effective in reducing friction. With few exceptions, bearings require lubrication to reduce wear and extend bearing life.

bearing speed factor - is a term that defines the relationship of the velocity at which a bearing rotates with the size of the bearing.


bearing clearance - the amount of space between the rollers and the raceways or the journal and the bearing surface.


bellows sealed valves - an elastic seal that can be compressed when pressure is applied used to reduce external leakage typically at a valve stem or actuator.


bench test - a test carried out on a component before it is released for use, to ensure that it works as designed.


bentonite thickener - composed mainly of silicon dioxide and aluminum oxide used to firm up greases. Usually have no dropping point as bentonite does not melt.

benzene - aromatic hydrocarbon consisting of six car­ bon atoms and six hydrogen atoms arranged in a hexagonal ring structure. See aromatic, hydrocarbon. It is used extensively in the petrochemical industry as a chemical intermediate and reaction diluent and in some applications as a solvent. Benzene is a toxic substance, and proper safety precautions should be observed in handling it.

Bernoulli’s Theorem - in hydraulics, a rise in fluid velocity is accompanied by a drop in static pressure and vice versa.


beta ratio - refers to the efficiency in which a given filter element removes particles of a given size.

bevel gear - see gears.


bhp - brake horsepower, the effective or available power of an engine or turbine, measured at the output shaft. It is equivalent to the calculated horsepower, less the power lost in friction.


biocide - a chemical substance or microorganism intended to destroy, deter, render harmless any organism by chemical or biological means.

biodegradation - the chemical breakdown of material s, such as petroleum products, by living organisms in the environment. The process depends on certain microorganisms, such as bacteria, yeast, and fungi, which break down molecules for sustenance. Certain chemical structures are more susceptible to microbial breakdown than others; vegetable oils, for example, will biodegrade more rapidly than petroleum oils. Most petroleum products typically will completely biodegrade in the environment within two months to two years.

bio-toxic - poisonous to the environment.


bitumen - any of various mixtures of viscous, brown-to-black hydrocarbons, such as asphalt, together with any accompanying non-metallic derivative such as sulfur or nitrogen compounds; may occur naturally or may be obtained as residues from refining processes.

black oil - lubricant containing asphaltic materials, used in heavy -duty equipment applications, such as mining and quarrying, where extra adhesiveness is desired.

bleeding - the separation of liquid lubricant from a lubricating grease. See syneresis.


blend - composite of two or more components mixed together to achieve desired physical and chemical properties. In petroleum product manufacture, a blend may consist of two or more base stocks (e.g., the blending of two solvent neutrals of different viscosities to make a product of intermediate viscosity), or a base stock combined with chemical additives. See batch blending and inline blending.


block grease - very firm grease manufactured in block form to be applied to certain large, open plain bearings, generally operating at slow speeds and moderate temperatures.


blocking point - lowest temperature at which waxed papers stick together, or block, sufficiently to injure the surface films and performance properties, as determined by test method ASTM D1465.

block penetration - see penetration (grease).


blow-by - in an internal combustion engine, seepage of fuel and gases past the piston rings and cylinder wall into the crankcase, resulting in crankcase oil dilution and deposit formation. See positive crankcase ventilation, dilution of engine oil.


blown asphalt - see asphalt.


blown rapeseed oil - see rapeseed oil.


blowout - uncontrolled eruption of gas, oil, or other fluids from a well to the atmosphere.

blowout preventer - equipment installed at the wellhead to prevent the escape of pressure, or pressurized material, from the drill hole.

BMEP - stands for brake mean effective pressure. It's the theoretical average pressure exerted on the pistons of a frictionless engine that matches the power output of the considered engine. It measures how efficiently an engine uses its piston displacement to perform work.

boiling range - temperature spread between the initial boiling point and final boiling point. See distillation test.


bomb oxidation stability - measure of the oxidation stability of greases and lubricating oils in separate tests: ASTM D942 (grease), ASTM D2272 (oil) and ASTM D2112 (electrical insulating oils). In all tests, the sample is placed in a container, or bomb, which is then charged with oxygen and pressurized; a constant elevated temperature is maintained. ASTM D2272 utilizes a rotating bomb, which is placed in a heated bath; the test therefore is commonly called the rotary bomb oxidation test. Oxidation stability is expressed in terms of pressure drop in a given time period (D942) or in terms of the time required to achieve a specified pressure drop (D2272, D2112).

borehole - the hole made by drilling, or boring, a well; also called well bore. See rotary drilling.


Bosch number - a measure of diesel smoke determined by passing the exhaust gas through a white filter paper. The darkening of the paper is determined using a reflectometer, and Bosch numbers are reported on a scale of 1 (clear) to 10 (black). See diesel fuel.


bottle-feed oiler - See oiler.


bottled gas - a gas pressurized and stored in a transportable metal container. See LPG.


bottoms - in refining, the high-boiling residual liquid (also called residuum) - including such components as heavy fuels and asphaltic substances - that collects at the bottom of a distillation column, such as a pipe still. See distillation, fuel oil.


boundary lubrication - a form of lubrication between two rubbing surfaces without development of a full-fluid lubricating film. See full fluid-film lubrication, ZN/P curve. Boundary lubrication can be made more effective by including additives in the lubricating oil that provide a stronger oil film, thus preventing excessive friction and possible scoring. There are varying degrees of boundary lubrication, depending on the severity of service. For mild conditions, oiliness agents may be used; these are polar compounds that have an exceptionally high affinity for metal surfaces. By plating out on these surfaces in a thin but durable film, oiliness agents prevent scoring und er some conditions that are too severe for a straight mineral oil. Compounded oils, which are formulated with polar fatty oils, are sometimes used for this purpose. Anti-wear additives are commonly used in more severe boundary lubrication applications. High quality motor oils contain anti-wear additives to protect heavily loaded engine components, such as the valve train. The more severe cases of boundary lubrication are defined as extreme pressure conditions; they are met with lubricants containing EP additives that prevent sliding surfaces from fusing together at high local temperatures and pressures.

Boyles gas law - a law stating that the pressure and volume of a gas have an inverse relationship when temperature is held constant.

BR - see polybutadiene rubber.


brake fluid - A type of hydraulic fluid used in hydraulic brake and hydraulic clutch applications in automobiles, motorcycles, light trucks. Often a synthetic oil due to the heat of operation encountered.

brake horsepower - see bhp.


brass - a yellow alloy of copper and zinc.

breakdown voltage - see dielectric strength.


breather - a vent or valve to release pressure or to allow air to move freely in and out of an enclosure.

bright stock - high-viscosity oil, highly refined and dewaxed, produced from residual stocks, or bottoms; used for blending with lower viscosity oils.

Brinell scale - a standardized material indentation hardness test in engineering and metallurgy. 

British thermal unit - see BTU.


bromine index - number of milligrams of bromine that will react with 100 grams of a petroleum product (test method ASTM D2710). Bromine index is essentially equivalent to bromine number x 1000.

bromine number - number of grams of bromine that react with 100 grams of a sample of a petroleum distillate. This gives an indication of its relative degree of reactivity, as determined by test method ASTM D1159. It can be used as an indicator of the relative number of olefins and di-olefins. These are double-bonded straight-chain or cyclic hydrocarbons. See bromine index.


bronze - a yellowish-brown alloy of copper with up to one-third tin.

Brookfield viscosity - apparent viscosity of an oil, as determined under test method ASTM D2983. Since the apparent viscosity of a non­-Newtonian fluid holds only for the shear rate (as well as temperature) at which it is determined, the Brookfield viscometer provides a known rate of shear by means of a spindle of specified configuration that rotates at a known constant speed in the fluid. The torque imposed by fluid friction can be converted to absolute viscosity units (centipoise) by a multiplication factor. See viscosity, shear stress. The viscosities of certain petroleum waxes and wax-polymer blends in the molten state can also be determined by the Brookfield test method ASTM D2669.

BS&W - abbreviation of " bottoms sediment and water," the water and other extraneous material present in crude oil. Normally, the BS&W content must be quite low before the oil is accepted for pipeline delivery to a refinery.

Btu (British thermal unit) - quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit, at 60°F and at a pressure of one atmosphere. See energy.


buffer solution - an aqueous solution consisting of a mixture of weak acid and its conjugate base. Its pH changes very little when a small amount of strong acid or base is added to it.

bulk appearance - visual appearance of grease when the undisturbed surface is viewed in an opaque container. Bulk appearance should be described in the following terms. Smooth - a surface relatively free of irregularities. Rough - a surface composed of many small irregularities. Grainy - a surface composed of small granules or lumps of soap particles. Cracked - showing surface cracks of appreciable number and magni­tude. Bleeding - showing free oil on the surface of the grease (or in the cracks of a cracked grease). See texture.


bulk delivery - large quantity of unpackaged petroleum product deliv­ered directly from a tank truck, tank car, or barge into a consumer's storage tank.

bulk modulus - measure of a fluid's resistance to compressibility; the reciprocal of compressibility.

bulk odor - odor of vapor emanating from bulk liquid quantities of a petroleum product; also referred to as impact odor. The odor remaining after the product has evaporated is called residual odor.


bulk temperature - in a heat transfer system, the temperature of the main stream of heat transfer fluid in the heating unit, as distinct from film temperature, which is the temperature of the slower moving layer of fluid in contact with the surface of the heating tube or coil. Film temperature may be far higher than bulk temperature and may exceed the maximum temperature for which the fluid is recommended. The differential between the two temperatures depends primarily on flow velocity, which is a function of the design of the installation and the flow properties of the fluid. These factors must be considered when selecting the proper heat transfer fluid.

Buna-N.- see nitrile rubber.


Buna S Material - often referred to as SBR. A family of synthetic rubber used most often in the manufacture of tires. Derived from styrene and butadiene.

bunker C fuel oil - see fuel oil.


burst pressure - is the pressure that an enclosed vessel like pipe or tube can handle before rupturing.

bushing - a type of bearing, a cylindrical lining designed to reduce friction and wear, often used as a casing for a shaft, pin or hinge.

butadiene rubber - see polybutadiene rubber.


butane - gaseous paraffinic hydrocarbon (C4H10), usually a mixture of iso and normal butane (see isomer, normal paraffin); also called, along with propane, liquefied petroleum gas (LPG).


butyl rubber - a synthetic rubber of isobutylene and isoprene. Used in application requiring an airtight seal.

butylene - any of three isomeric (see isomer) flammable, gaseous hydrocarbons of the molecular structure C4H8; commonly derived from hydrocarbon cracking.


butyl rubber (IIR) - synthetic rubber, produced by copolymerization of iso butylene with isoprene or butadiene (see polymer). It is resistant to weather and heat, has low air-permeability and low resiliency; used in the manufacture of cable insulation, tubeless tire inner liners and other appli­cations requiring good weather resistance and air retention.

by-pass filtration - an auxiliary filtration system, designed to augment the main system filter. Continually remove contaminants from the fluid without impact main oil flow or filtration.


by-pass valve - typically a valve used to divert flow of a fluid. Often acts as a backup to allow continuous operation in case failure or damage occurs to the main pipeline.


C (Celsius) - see temperature scales.


calcium soap grease - see grease.


calorie - term applicable either to the gram calorie or the kilocalorie. The gram calorie is defined as the amount of heat required at a pressure of one atmosphere to raise the temperature of one gram of water one degree Celsius at l5°C. The kilocalorie is the unit used to express the energy value of food; it is defined as the amount of heat required at a pressure of one atmosphere to raise the temperature of one kilogram of water one degree Celsius; it is equal to 1000-gram calories. See energy.


calorific value - see heat of combustion.


carbonizable substances - petroleum constituents detectable in white oil, petrolatum, and paraffin wax. This detection occurs when these products mix with concentrated sulfuric acid, discoloring the acid. This process is detailed in ASTM D565 (for white oil and petrolatum).

carbon monoxide (CO) - colorless, odorless, poisonous gas, formed by the incomplete combustion of any carbonaceous material (e.g., gasoline, wood, coal). CO is the most widely distributed and most commonly occurring air pollutant, with motor vehicles being the primary source of man-made emissions, although emission controls are reducing the automobile's contribution. It is estimated that more than 90% of atmo­spheric CO comes from natural sources, such as decaying organic matter. See catalytic converter, emissions (automotive), pollutants.


carbon residue - percent of coked material remaining after a sample of oil has been exposed to high temperatures under test method ASTM D189 (Conradson), D524 (Ramsbottom), or D4530 (Micro Carbon); hence, a measure of coke-forming tendencies. Results should be interpreted cautiously, as there may be little similarity between test conditions and actual service conditions.

carbon type analysis - an empirical assessment of rubber process oil composition. This analysis reveals the percentage of carbon atoms in aromatic, naphthenic, and paraffinic components, respectively. See rubber oil, aromatic, naphthene, paraffin, Corbett Analysis of Asphalt.


carbonyl - the divalent radical CO, which occurs in various organic substances, such as organic acids; also, any metal compound containing this radical. Carbonyls are highly reactive and considered to be catalyst poisons when present in solvents used as reaction diluents in polyolefin plastics manufacture.

carburetor - device in an internal combustion engine that atomizes and mixes fuel with air in the proper pro­portion for efficient com­bustion at all engine speeds, and controls the engines power output by throttling, or metering, the air-fuel mixture admitted to the cyl­inders. The automobile car­buretor is a complex mecha­nism designed to compensate for many variables over a wide range of speeds and loads. Intake air is drawn through the venturi, a constricted throat in the air passage that causes a pressure reduction in the air stream, which draws fuel from the carburetor bowl through either the main jet or the idle jet. The fuel is atomized by the high-velocity air, and the resulting air-fuel mixture is piped through the intake manifold to the individual cylinders, where it is burned. A throttle plate between the venturi and the cylinders controls power and speed by controlling the volume of air-fuel mixture reaching the cylinders. The dissipation factor in an electrical system is denoted by the tangent of the loss angle. It could also be denoted by the cotangent of the phase angle. This factor measures electrical loss due to imperfect oil insulation surrounding the electrical system. The degree of loss is determined by the ASTM D924 test method. During cold starting, a choke (or butterfly valve) restricts airflow to the carburetor, thus enriching the mixture for faster starting. The choke on most automotive engine carburetors is operated automatically by a thermostatic spring, which opens the choke as the engine warms up. See fuel injection, supercharger.


carburetor icing - freezing of the moisture in hum id air inside the carburetor, restricting air supply to the engine and causing it to stall. The air is brought to freezing by the chilling effect of vaporizing fuel. Carburetor icing is most likely to occur when the air temperature is between 3°C and 13°C (38°F to 55°F); if the ambient temperature were higher, the moisture would not freeze, and if it were lower, the absolute humidity would not provide sufficient moisture. Carburetor icing can be prevented by using a gasoline with an anti-icing additive.


carcinogen - cancer causing substance. Certain petroleum products are classified as potential carcinogens under OSHA criteria. Suppliers are required to identify such products as potential carcinogens on package labels and Material Safety Data Sheets.


carrier - a liquid, such as water, solvent, or oil, in which an active ingredient is dissolved or dispersed.

CAS (Chemical Abstract Service) Registry Numbers - identifiers given to chemical substances by the Chemical Abstract Service of the American Chemical Society. The Environmental Protection Agency uses these numbers. They help with registering chemicals under the 1976 federal Toxic Substances Control Act. CAS numbers are assigned to generic refinery process streams, such as kerosene and lube base stocks, that contain no additives. Petroleum products containing additives are termed "mixtures" by the TSCA and, as such, do not have CAS numbers. All chemical substances used in such mixtures are assigned CAS numbers and must be listed with the EPA by the refiner or the additive supplier.

casing - steel pipe placed in a borehole as drilling progresses, to prevent the wall of the hole from caving in. See rotary drilling.


catalyst - substance that causes or speeds up a chemical reaction without itself undergoing an associated change; catalysts are important in a number of refining processes.

catalytic converter - an emissions control device, incorporated into an automobile's exhaust system, containing catalysts - such as platinum, palladium, or rhodium - that reduce the levels of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides(NOx) emitted to the air. In the catalytic converter, HC and CO are oxidized to form carbon dioxide (CO2), and NOx are reduced to nitrogen and oxygen. Three-way catalytic converters that control all three substances require associated electronic controls for precise regulation of oxygen levels in the exhaust gas. Catalytic converters are also effective in removing PNA (polynuclear aromatic) hydrocarbons. Cars equipped with catalytic converters require unleaded gasoline, since the lead in tetraethyl lead, an anti-knock com­ pound, is a catalyst "poison." See emissions (automotive), hydrocarbon emissions, pollutants, lead alkyl.


catalytic cracking - in refining, the breaking down at elevated tempera­tures of large, high-boiling hydrocarbon molecules into smaller mol­ecules in the presence of a catalyst. The principal application of catalytic cracking is the production of high-octane gasoline, to supplement the gasoline produced by distillation and other processes. Catalytic cracking generates heating oil components and hydrocarbon feedstocks. The latter includes substances such as propylene and butylene, used in polymerization, alkylation, and petrochemical processes.

cationic emulsified asphalt - see emulsified cationic asphalt.


caustic washing (scrubbing) - treatment of a petroleum liquid or gas with a caustic alkaline material (e.g., sodium hydroxide) to remove hydrogen sulfide, low-weight mercaptans, and other acidic impurities. See alkali.


cavitation - formation of a vapor pocket (or bubble) due to lowering of pressure in a liquid, often because of a solid body, such as a propeller or piston, moving through the liquid; also, the pitting or wearing of a solid surface as a result of the collapse of a vapor bubble. Cavitation can occur in a hydraulic system because of low fluid levels producing tiny bubbles that expand explo­sively at the pump outlet, causing metal erosion and eventual pump destruct ion.

Celsius (°C) - see temperature scales.


centigrade - see temperature scales.


centipoise - see viscosity.


centistoke - see viscosity.


centralized lubrication - automatic dispensing of grease or oil from a reservoir to the lubricated parts on one or more machines. Flow is maintained by one or more pumps, and the amount of lubricant supplied to each point can be regulated by individual metering devices. Such a system provides once-through lubrication. See mechanical lubrication, oil mist lubrication.


centrifugal - movement outward from the center. See compressor, pump.


CERCLA - See Comprehensive Environmental Response, Compensa­tion and Liability Act.


Certificate of Analysis (C of A) - list of laboratory test results that the supplier affirms to be representative of the quality of a product shipped to a particular customer.

cetane - colorless liquid hydrocarbon, C16H34, used as a standard in determining diesel fuel ignition performance. See cetane number.


cetane improver - additive for raising the cetane number of a diesel fuel.

cetane index - an approximation of cetane number based on diesel fuel density (kilograms/liter) at 15°C and distillation temperatures.

cetane number - measure of the ignition quality of a diesel fuel, expressed as the percentage of cetane that must be mixed with liquid methylnaphthalene to produce the same ignition performance as the diesel fuel being rated, as determined by test method ASTM D613. A high cetane number indicates shorter ignition lag and a cleaner burning fuel. See cetane, cetane index, diesel index.


chain oil - uninhibited mineral oil, used to lubricate chain saw bars and chains and other equipment with non-critical requirements or where oxidizing influences are not severe. See inhibitor, oxidation.


channeling - formation of a channel in a lubricant by a lubricated element, such as a gear or rolling contact bearing, leaving shoulders that serve as a seal and reservoir. This phenomenon is usually desirable as a channel that is too deep or permanent could cause component failure.

Chemical Abstract Service Registry Numbers - see CAS Registry Numbers.


chlorinated wax - wax treated with chlorine gas to form straight-chain hydrocarbons with a relatively high chlorine component. Chlori­nated waxes are used primarily as polyvinyl chloride plasticizers, extreme-pressure additives for lubricants, and formulation compo­nents for many cutting fluids.


chlorine - see halogen.


Christmas tree - structure of valves, fittings, and pressure gauges at the top of a well to control the flow of oil and gas.

chromatography - method of separating and analyzing the com­ponents of a chemical mixture; commonly used in the analysis of many types of petroleum products. The test sample is introduced into the chromatograph by means of an injection port, which leads to a column inside an oven. In gas chromatography the sample is volatilized and carried into the column by pressurized inert gas. The sample components are absorbed into a liquid (called the stationary phase) present inside the column. Regulating the oven tem­perature causes the sample components to reach the detector at the column outlet in order of respective boiling points. Each component is identified on the basis of its retention time in the column. The data are shown on a chromatogram in the form of peaks, whose heights represent the concen­tration of the respective components. In liquid chromatography, the sample is carried through the column by an inert liquid and passes through a packing of tiny spheres coated with a stationary phase. The time required for specific components to emerge from the column is directly propor­tional to their degree of solubility in the stationary phase. Each component is identified on the basis of its retention time in the column. See clay/silica gel analysis, ferrography, infrared analysis, mass spectrometer, particle count, spectrographic analysis.


chronic effect – cumulative physiological damage resulting from pro­longed exposure or series of exposures to a toxic substance. Also known as chronic toxicity. See acute effect, health hazard.


chronic toxicity - see chronic effect.


circulating lubrication system - system in which oil is recirculated from a tank to the lubricated parts, in most cases requiring a pump to maintain circulation. Circulating lubrication makes possible extended lubricant use, and usually requires a high-quality rust-and-oxidation­ inhibited (R&O) oil.

clay filtration refining pro­cess using fuller's earth (acti­vated clay) or bauxite to adsorb minute solids from lubricating oil, as well as remove traces of water, acids, and polar com­ pounds. See adsorption.


Cleveland Open Cup (COC) - method (ASTM D92) for determining the flash point and fire point of all petroleum. products except fuel oil and products with flash points below 79°C (1 7 5°F). The oil sample is heated in a precisely specified brass cup containing a thermometer. At specified intervals a small flame is passed across the cup. The lowest temperature at which the vapors above the cup briefly ignite is the flash point; the temperature at which the vapors sustain combustion for at least five seconds is the fire point. See Tag open cup.


Cleveland closed cup - method (D93) for determining the flash point of fuels, solvents, cutback asphalts, and some light lube fractions, utilizing a covered container in which the test sample is heated and periodically exposed to a small flame introduced through a shuttered opening. The lowest tempera­ture at which the vapors above the sample briefly ignite is the flash point. See Pensky-Martens closed tester, Tag closed tester.


cloud point - temperature at which a cloud or haze of wax crystals appears at the bottom of a sample of lubricating oil in a test jar, when cooled under conditions prescribed by test method ASTM D2500. Cloud point is an indicator of the tendency of the oil to plug filters or small orifices at cold operating temperatures. It is very similar to wax appear­ance point.


CMS asphalt - see emulsified cationic asphalt.


coastal oil - common term for any predominantly naphthenic crude derived from fields in the Texas Gulf Coast area.

coefficient of friction - see friction.


cohesion - molecular attraction causing substances to stick together, a factor in the resistance of a lubricant, especially a grease, to flow.

coke - by-product of the coking process, primarily carbon with varying concentrations of nickel, vanadium, and sulfur, and produced either as chunks or sand-like grains. Coke with relatively low metal and sulfur content is used as a feedstock in the manufacture of anodes for aluminum and steel production; coke with higher metal and sulfur concentrations is commonly used as a coal substitute.

coking - in petroleum refining, the conversion of high-boiling residuum, und er heat and pressure, to higher-value naphthas, gas oils, and other light products. The process produces as a by-product a dry, predominantly carbonaceous residue called coke.


cold-end corrosion - corrosion due to the acid-forming condensation of sulfur trioxide (S03) on cool surfaces of a boiler, especially the cooler parts of the chimney and the air heater; also called low-temperature corrosion. It can be prevented or minimized by using resistant alloys, by operating at low excess air levels (which reduces SOproduction), or by operating at higher stack temperatures.

cold-flow improver - additive to improve flow of diesel fuel in cold weather. In some in stances, a cold-flow improver may improve operabil­ity by modifying the size and structure of the wax crystals that precipitate out of the fuel at low temperatures, permitting their passage through the fuel filter. In most cases, the additive depresses the pour point, which delays agglomeration of the wax crystals, but usually has no significant effect on diesel engine performance. A preferred means of improving cold flow is to blend kerosene with the diesel fuel, which lowers the wax appearance point by about 1°C (2°F) for each 10% increment of kerosene added.

cold sett grease - see sett grease.


colloid - suspension of finely divided particles, 5 to 5000 angstroms in size, in a gas or liquid, that do not settle and are not easily filtered. Colloids are usually ionically stabilized by some form of surface charge on the particles to reduce the tendency to agglomerate. A lubricating grease is a colloidal system, in which metallic soaps or other thickening agents are dispersed in, and give structure to, the liquid lubricant.

color scale - standardized range of colors against which the colors of petroleum products may be compared. There are several widely used systems of color scales, including: ASTM scale (ASTM D1500), the most common scale, used extensively for industrial and process oils. Also, Tag-Robinson colorimeter, used with solvents, waxes, industrial and process oils. Saybolt chromometer (ASTM D156), used with white oils, naphthas, waxes, fuels, kerosene, solvents. Lovibond tintometer, for USP petrolatum, sulfonates, chemicals. The Platinum- Cobalt (APHA) system (ASTM D1209), for lacquer solvents, diluents, petro­chemicals. These scales serve primarily as indicators of product unifor­mity and freedom from contamination.

combustible liquid - see flammable liquid.


combustion - rapid oxidation of a fuel (burning). The products of an ideal combustion process are water (H2O) and carbon dioxide (CO2); if combustion is incomplete. Some carbon is not fully oxidized, yielding carbon monoxide (CO). A stoichiometric combustible mixture contains the exact quantities of air (oxygen) and fuel required for complete combustion. For gasoline, this air-fuel ratio is about 15:1 by weight. If the fuel concentration is too rich or too lean relative to the oxygen in the mixture, combustion cannot take place. See explosive limits, internal combustion engine.


combustion chamber - in an internal combustion engine, the volume, bounded by the top of the piston and the inner surface of the cylinder head, in which the air-fuel charge ignites and burns. Valves and spark plugs are fitted into the combustion chamber.

commercial oils - see AP/ Engine Service Categories.


commodity product - non-proprietary product that is in distinguishable from comparable competitive products in formulation, quality, and per­formance. Toluene and heavy fuel oil are common examples. See fungible.


complex soap - see grease.


compounded oil - mixture of a petroleum oil with animal or vegetable fat or oil. Compounded oils have a strong affinity for metal surfaces; they are particularly suitable for wet-steam conditions and for applications where lubricity and extra load-carrying ability are needed. They are not generally recommended where long-term oxidation stability is required.

Comprehensive Environmental Response, Compensation and Liabil­ity Act (CERCLA) - also called the Superfund, this U.S. statute, admin­istered by the EPA. It provides funding and enforcement authority for cleaning up existing hazardous waste sites and for responding to hazard­ous substance spills. CERCLA encompasses industrial, commercial, and non-commercial spills to water, ground water, soil, and air. Petroleum and natural gas are excluded from the CERCLA definition of "hazardous", but are covered by a range of other health and environmental legislation. See Superfund Amendments and Reauthorization Act, Toxic Substance Con­trol Act, Resource Conservation and Recovery Act.


compression ignition - the form of ignition that initiates combustion in a diesel engine. The rapid compression of air within the cylinders gener­ates the heat required to ignite the fuel as it is injected. See after-running internal combustion en­gine.


compression-ignition engine - diesel engine. See internal combustion engine.


compression ratio - in an internal combustion engine, the ratio of the volume of the combus­tion space in the cylinder at the bottom of the piston stroke to the volume at the top of the stroke. High-compression-ratio gasoline engines require high octane fuels (see octane number). Not to be confused with the pressure ratio of a compressor.


compressor - mecha­nism through which force is applied to a gas. There are three basic types of compressors: dynamic, reciprocating, and ro­tary. A dynamic compres­sor (also called kinetic) may be either centrifugal or axial flow. A centrifu­gal compressor uses the rotation of an impeller and a shaft to push the gas outward. An axial flow­ type uses the rotation of a propeller-type blade to move the gas in the axial direction of the shaft. A reciprocating compres­sor employs a piston and cylinder to compress the gas. A rotary compressor uses a rotating vane or screw. Both reciprocat­ing and rotary-type com­pressors are also known as positive displacement compressors. To reduce temperature, rise and minimize oil oxidation and deposit buildup, some compressors are multi-stage, raising the air to the desired pres­sure in several steps through a sequence of chambers and cooling the air between steps. Be­ cause gas compression generates heat, a com­pressor lubricant should have high oxidation sta­bility, as well as good demulsibility, rust and cor­rosion inhibition and anti-­foam properties. See anti­-foam agent, corrosion, inhibitor, inter-cooling, and rust inhibitor.


concrete form coating - an oil, wax, or grease applied to wooden or metal concrete forms to keep the hardened con­crete from adhering to the forms. The liquid mate­rials are also called form oil.


condensate - in refin­ing, the liquid produced when hydrocarbon va­pors are cooled. In oil and gas production, the term applies to hydrocar­bons that exist in gas­eous form under reser­voir conditions, but con­dense to a liquid when brought to the surface.

congealing point - the temperature at which molten wax ceases to flow, as measured by test method ASTM D938; of importance where storage or application temperature is a critical factor. See melting point of wax.


coning oil - lubricant, containing emulsifiers and anti-static agents, applied to synthetic-fiber yarn to reduce snagging, and pulling as the yarn is run off a cone, and to facilitate further processing. See fiber lubricant.


Conradson carbon residue - see carbon residue.


conservation - see energy conservation.


consistency (grease) - a basic property describing the softness or hardness of a grease, i.e., the degree to which a grease resists deformation under the application of force. Consistency is measured by means of a cone penetration test. See penetration (grease). The consistency of a grease depends on the viscosity of the base oil and the type and proportion of the thickener. It may also be affected by recent agitation; to take this phenom­enon into consideration, a grease may be subjected to working (a standard churning process) prior to measuring its penetration value. See NLGI consistency grades.


copolymer - see polymer.


copper strip corrosion - the tendency of a petroleum product to corrode cuprous metals, as determined by test method ASTM D130; the corrosion stains on a test copper strip are matched against standardized corroded strips.

Corbett Analysis of Asphalt - former common name for ASTM D4124, Separation of Asphalt into Four Fractions (asphaltenes, saturates, polar aromatics, and naphthene aromatics). See polar compound, satu­rated hydrocarbons.


corrosion - chemical attack on a metal or other solid by contaminants in a lubricant. Common corrosive contaminants are: (1) water, which causes rust, and (2) acids, which may form as oxidation products in a deteriorating oil, or may be introduced into the oil as combustion by-products in piston engines. See corrosion inhibitor.


corrosion inhibitor additive for protecting lubricated metal surfaces against chemical attack by water or other contaminants. There are several types of corrosion inhibitors. Polar compounds wet the metal surface preferentially, protecting it with a film of oil. Other compounds may absorb water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Another type of corrosion inhibitor com­bines chemically with the metal to present a non-reactive surface. See rust inhibitor.


coupling - See flexible coupling.


cp (centipoise) - see viscosity.


CPSC (Consumer Products Safety Commission) - a federal commission that oversees legislation on consumer product safety. They administer the Consumer Product Safety Act, Federal Hazardous Substances Act, Flammable Fabrics Act, Poison Prevention Packaging Act, and the Refrigeration Safety Act.


cracking - petroleum refining process in which large-molecule liquid hydrocarbons are converted to small-molecule, lower-boiling liquids or gases; the liquids leave the reaction vessel as unfinished gasoline, kerosene, and gas oils. At the same time, certain unstable, more reactive molecules combine into larger molecules to form tar or coke. The cracking reaction may be carried out under heat and pressure alone (thermal cracking), or in the presence of a catalyst (catalytic cracking).


crackle test - method for obtaining a semi-quantitative estimate of the amount of trace water present in a finished lubricant. A portion of the lubricant sample is poured into a metal pan or dipper that is heated at a specified temperature. One or more distinct pops or crackles will be heard, and bubbles will form on the surface if water is present. See Karl Fischer Method.


crankcase oil - see engine oil.


crop oil agricultural oil, lower in quality than orchard spray oil; commonly used as an adjuvant in herbicide spray formulations.

CRS asphalt - see emulsified cationic asphalt.


crude oil - complex, naturally occurring fluid mixture of petroleum hydrocarbons, yellow to black in color, and containing small amounts of oxygen, nitrogen and sulfur derivatives and other impurities. Crude oil was formed by the action of bacteria, heat, and pressure on ancient plant and animal remains, and is usually found in layers of porous rock such as limestone or sandstone capped by an impervious layer of shale or clay that traps the oil (see reservoir). Crude oil varies in appearance and hydrocar­bon composition depending on the locality where it occurs, some crudes being predominantly naphthenic, some paraffinic, and others asphaltic. Crude is refined to yield petroleum products. See asphalt, distillation, hydrocarbon, sour crude, sweet crude, naphthene, paraffin.


CSS asphalt - see emulsified cationic asphalt.


cSt (centistoke) - see viscosity.


cut - segregated part, or fraction, separated from crude oil in the distillation process.

cutback asphalt- a solution of asphalt cement and a petroleum diluent. Upon exposure to the atmosphere, the diluent evaporates, leaving the asphalt cement to perform its function. There are three asphalt grades. First, RC asphalt, which is rapid curing cutback asphalt, consisting of asphalt cement and a high volatility naphtha-type diluent. Second, MC asphalt. This is a medium-curing asphalt composed of asphalt cement and medium volatility kerosene-type diluent. Finally, SC asphalt. This is slow-curing cutback asphalt. It includes asphalt cement and a low-volatility oil. For industrial uses, oxidized asphalts can be blended with a petroleum diluent to meet the specific requirements of coatings, mastics, etc. See asphalt, solvent-cutback.


cutting fluid - fluid, usually petroleum-based, for cooling and lubricat­ing the tool and work in metal cutting operations. Some flu ids are fortified with EP additives to facilitate cutting of hard metals, to improve finishes, and to lengthen tool life. Cutting fluids that react chemically with metal surfaces are called active oils; sulfurized oils, for example, have improved load-carrying properties, but may stain non-ferrous metals. Some cutting oils are transparent to provide a better view of the work. Most cutting fluids fall into four basic categories. 1) straight oils, mineral oils blended with fatty oils for good wetting and penetrating characteristics and a good, machined finish. 2) emulsifiable (soluble) oils, mineral oils dispersed as minute droplets in water combine lubricating properties of oil with water's cooling properties. Emulsifiable oils are subject to bacterial action and resultant odors, they may contain a bactericide. 3) synthetic fluids, blends of chemical agents in water for improved machining speed, cooling, and tool life. 4) semi-synthetic fluids, water­ dilutable fluids that combine the lubricity of soluble oils with the advan­tages of synthetics. See metalworking lubricant.


cyclic hydrocarbon - hydrocarbon in which the carbon atoms are joined in rings.

cycloalkane - see naphthene.


cycloparaffin - see naphthene.


cylinder oil - lubricant for independently lubricated cylinders, such as those of steam engines and air compressors, also used for lubrication of valves and other elements in the cylinder area. Steam cylinder oils are available in a range of grades with high viscosities to compensate for the thinning effect of high temperatures; of these, the heavier grades are formulated for super-heated and high-pressure steam, and the less heavy grades for wet, saturated, or low-pressure steam. Some grades are compounded for service in excessive moisture; see compounded oil.


deasphalting - refining step for removal of asphaltic compounds from heavy lubricating oils. Liquid propane, liquid butane, or a mixture of the two is used to dilute the oil and precipitate the asphalt.


demerit rating - an arbitrary numerical system sometimes used in engine oil assessments. This method evaluates the deposit levels after testing an engine oil's detergent-dispersant properties. On a scale of zero to 10, the higher the number, the heavier the deposits. A more commonly used method of evaluating engine cleanliness is merit rating. See engine deposits.


demulsibility - ability of an oil to separate from water, as determined by test method ASTM D1401. Demulsibility is an import ant consideration in lubricant maintenance in many circulating lubrication systems.


demulsifier additive that promotes oil - water separation in lubricants that are exposed to water or steam. See demulsibility.


denaturing oil - unpalatable oil, commonly kerosene or No. 2 heating oil, required to be added to food substances condemned by the U.S. Department of Agriculture, to ensure that these substances will not be sold as food or consumed as such.

density - see specific gravity.


de-oiling - removal of oil from petroleum wax; a refinery process usually involving filtering or pressing a chilled mixture of slack wax and a solvent that is miscible in the oil, to lower the oil content of the wax. See dewaxing.


Department of Transportation (DOT) - federal agency with regula­tory responsibility for all modes of domestic transportation, including pipelines; responsibilities include regulating the transport of hazardous material. The DOT's hazardous material regulations are contained in Title 49 of the Code of Federal Regulations (49 CFR). See International Air Transport Association, International Civil Aviation Organization, Inter­national Maritime Organization.


depletion allowance - a reduction in U.S. taxes on producers of minerals, including petroleum, to compensate for the exhaustion of an irreplaceable capital asset.

deposits - see engine deposits.


dermatitis - inflammation of the skin; can be caused by contact with many commercial substances, including petroleum products. Oil and grease in contact with the skin can result in plugging of sweat glands and hair follicles or defatting of the skin, which can lead to dermatitis. Dermatitis can be prevented in such cases by avoiding contact with the causative substances, or, if contact occurs, by promptly washing the skin with soap, water, and a soft skin brush. Clothes soaked with the substance should be removed and laundered before re-use.

detergent - important component of engine oils and some industrial lubricants, such as paper machine oils and hydraulic fluids; helps control deposits by preventing contaminants of combustion from directly contact­ing metal surfaces and, in some cases, by neutralizing acids. A detergent is usually a metallic (commonly calcium, or magnesium) com­pound, such as a sulfonate, phosphonate, thiophosphate, phenate, or salicylate. Because of its metallic composition, a detergent leaves a slight ash when the oil is burned. A detergent is normally used in conjunction with a dispersant. See ash content, detergent-dispersant, engine deposits.


detergent-dispersant - engine oil additive that is a combination of a detergent and a dispersant; important in preventing the formation of sludge and other engine deposits.


detonation - see knock.


dewaxing - removal of paraffin wax from lubricating oils to improve low temperature properties, especially to lower the cloud point and pour point. In solvent dewaxing, the oil is diluted with a solvent that has a high affinity for oil, chilled to precipitate the wax, filtered to remove the wax, stripped of solvent, and dried. In hydro-dewaxing (also called cat-dewaxing), the oil is contacted with hydrogen at elevated temperature and pressure over a special catalyst that selectively cracks the normal paraffins, which are converted to methane, ethane, and propane. The oil is steam stripped and dried.

dibasic acid ester (di-ester) - synthetic lubricant base; an organic ester, formed by reacting a dicarboxylic acid and an alcohol; properties include a high viscosity index (V.I.) and low volatility. With the addition of specific additives, it may be used as a lubricant in compressors, hydraulic systems, and internal combustion engines.


dielectric loss - see power factor.


dielectric - non-conductor of electricity, such as electrical insulating oil for transformers. See electrical discharge machining fluid, power factor.


dielectric strength (breakdown voltage) - minimum voltage required to produce an electric arc through an oil sample, as measured by test method ASTM D877; hence, an indication of the insulating (arc preventive) properties of an electrical insulating oil. A low dielectric strength may indicate contamination, especially by water. See power factor.


diesel engine - see internal combustion engine.


diesel fuel - that portion of crude oil that distills out within the temperature range of approximately 200°C (392°F) to 370°C (698°F), which is higher than the boiling range of gasoline. See distillation. Diesel fuel is ignited in an internal combustion engine cylinder by the heat of air under high compression - in contrast to motor gasoline, which is ignited by an electrical spark. Because of the mode of ignition, a high cetane number is required in a good diesel fuel. Diesel fuel is close in boiling range and composition to the lighter heating oils. The American Society for Testing and Materials (ASTM) established two diesel fuel grades. These are Diesel 1 and Diesel 2. Diesel 1 is a kerosene-type fuel. It's lighter, more volatile, and burns cleaner than Diesel 2. It's used in engines were speed and load change frequently. Diesel 2 is used in industrial and heavy mobile service. Diesel fuel is also widely used in drilling mud formulations. See drilling oil.


diesel index - an approximation of the cetane number of a distillate fuel: the product of the API gravity (see specific gravity) and the aniline point (°F) divided by 100. Fuels of unusual composition may show erroneous cetane numbers by this method. See cetane index.


dieseling - see after-running.


diester - see dibasic acid ester.


Dilchil® - wax crystallization method used in ketone dewaxing of lubricating oils. This advanced solvent dewaxing technology was developed and licensed by Exxon Research and Engineering. See ketone.


diluent - a usually inert liquid or solvent, used to dilute, carry, or increase the bulk of some other substance. Petroleum oils and solvents are commonly used as diluents in such products as paints, pesticides, and additives. See reaction diluent.


dilution of engine oil - thinning of engine oil by seepage of fuel into the crankcase, which indicates the volume percentage of fuel in the sample. Dilution is detrimental to lubrication and may indicate defective engine components such as worn piston rings - or improper fuel system adjustment.

dimer - see polymerization.


diolefin - highly reactive straight-chain hydrocarbon with two double bonds between adjacent carbon atoms. See olefin.


dispersant - engine oil additive that helps prevent sludge, varnish, and other engine deposits by keeping particles suspended in a colloidal state (see colloid) within the bulk oil. Dispersants are normally used in conjunc­tion with detergents. A dispersant can be distinguished from a detergent in that the former may be non-metallic and, thus, does not leave an ash when the oil is burned; hence, the term ashless dispersant.


dispersion - minute discrete particles suspended in a liquid, a gas, or a solid. Though it may have the general characteristics of a colloid, a dispersion is not necessarily a truly homogeneous mixture.

dissipation factor -in an electrical system is denoted by the tangent of the loss angle. It could also be denoted by the cotangent of the phase angle. This factor measures electrical loss due to imperfect oil insulation surrounding the electrical system. The degree of loss is determined by the ASTM D924 test method. Dissipation factor is related to power factor. See electrical insulating oil.


distillate - any of a wide range of petroleum products produced by distillation, as distinct from bottoms, cracked stock (see cracking), and natural gas liquids. In fuels, a term referring specifically to those products in the mid-boiling range, which include kerosene, turbo fuel, and heating oil - also called middle distillates and distillate fuels. In lubricating oils, a term applied to the various fractions separated under vacuum in a distillation tower for further processing (lube distillate).

distillate fuel - see distillate.


distillation (fractionation) - the primary refining step, in which crude oil is separated into fractions, or components, in a distillation tower, or pipe still. Heat is typically applied at the bottom of the tower. This causes oil vapors to rise through cooler tower levels. Here they condense onto plates and are drawn off based on their condensation temperatures or boiling points. The lighter, low-boiling point fractions exit higher in the tower. The primary fractions, from low to high boiling point, are hydrocarbon gases (e.g., ethane, propane); naphtha (e.g., gasoline); kerosene, diesel fuel (heating oil); and heavy gas oil for cracking. Heavy materials remaining at the bottom are called the bottoms, or residuum, and include such components as heavy fuel oil (see fuel oil) and asphaltic substances (see asphalt). Those fractions taken in liquid form from any level other than the very top or bottom are called side-stream products; a product, such as propane, removed in vapor form from the top of the distillation tower is called overhead product. Distillation may take place in two stages. First, the lighter fractions - gases, naphtha, and kerosene - are recovered at essentially atmospheric pressure. Next, the remaining crude is distilled at reduced pressure in a vacuum tower, causing the heavy lube fractions to distill at much lower temperatures than possible at atmospheric pressure. This permits more lube oil to be distilled without the molecular cracking that can occur at excessively high temperatures. See hydrocracking.


distillation test - method for determining the full range of volatility characteristics of a hydrocarbon liquid by progressively boiling off (evaporating) a sample under controlled heating. Initial boiling point (IBP) is the fluid temperature at which the first drop falls into a graduated cylinder after being condensed in a condenser connected to a distillation flask. Mid-boiling point (MBP) is the temperature at which 50% of the fluid has collected in the cylinder. Dry point is the temperature at which the last drop of fluid disappears from the bottom of the distillation flask. Final boiling point (FBP) is the highest temperature observed. Front-end volatility and tail-end volatility are the amounts of test sample that evaporate, respectively, at the low and high temperature ranges. If the boiling range is small, the fluid is said to be narrow cut, that is, having components with similar volatilities; if the boiling range is wide, the fluid is termed wide cut. Distillation may be carried out by several ASTM test methods, including ASTM D86, D850, D1078, and D1160.

distillation tower - see distillation.


dN factor - or speed factor, is calculated by multiplying a rolling-contact bearing's bore size, in millimeters, by the journal speed, in rpm. The journal here refers to the supported shaft or axle. The dN factor, along with the operating temperature, helps determine the suitable viscosity of the bearing lubricating oil.

dolomite - sedimentary rock similar to limestone, but rich in magnesium carbon ate. Dolomite is sometimes a reservoir rock for petroleum.


drag-reducing additive (DRA) - high-molecular-weight polymer in a hydrocarbon solvent, used to improve the flow properties of crude oil or fuel products in a pipeline. Minute quantities of the additive can increase pipeline throughput by up to 50%. See hydrocarbon, molecular weight.


drain interval - See oil drain interval.


drawing - shaping metal by pulling it through a graduated series of dies until the material has been reduced to the desired diameter. Common products of this process are electrical wiring and wire springs. See drawing, metalworking lubricant.


drawing compound - in metal forming, a lubricant for the die or blank used to shape the metal; often contains EP additives to increase die life and to improve the surface finish of the metal being drawn. See drawing, metalworking lubricant.


drilling - see rotary drilling.


drilling fluid - also called drilling mud. See drilling oil.


drilling mud - see mud.


drilling oil- fluid component of mud for rotary drilling of oil wells. Diesel fuel is most commonly used in this application; however, there is a trend toward the use of high-quality mineral oils with lower viscosity for faster drilling rates, higher flash point for improved safety, and low aromatics content for reduced potential toxicity to workers and the environment.

drop-feed oiler - See oiler.


dropping point - lowest temperature at which a grease is sufficiently fluid to drip, as determined by test method D2265; hence, an indication of whether a grease will flow from a bearing at operating temperatures. The test is of limited significance in predicting overall service performance.

dry point - see distillation test.


dumbbell blend - mixture of hydrocarbons, usually two components, that have markedly different volatilities, viscosities, or other properties. See volatility, viscosity.


dynamic demulsibility - test of water separation properties of an oil, involving continuous mixture of oil and water at elevated temperatures in an apparatus that simulates a lubricating oil circulating system. Samples are then drawn off both the top and bottom of the test apparatus. Ideally, the top sample should be 100% oil, and the bottom 100% water. Because of the severity of the test conditions, separation is virtually never com­plete.

dynamometer - instrument used to measure force or power, such as the horsepower developed by an internal combustion engine. Horsepower can be determined by measuring the torque (turning power) produced by the rotating output shaft or by placing the driving wheels of a car on large rollers that drive a dynamometer. The latter method is often regarded as a better indicator of actual road performance. The dynamometer can be loaded to put the engine through a range of simulated rating conditions. Dynamometer testing is commonly employed to assess the performance characteristics of automotive fuels and lubricants.



EDM - See electrical discharge machining.

Elasto-hydrodynamic (EHD) lubrication - lubrication phenomena occurring during elastic deformation of two non-conforming surfaces under high load. A high load carried by a small area (as between the ball and race of a rolling contact bear­ing) causes a temporary increase in lubri­cant viscosity as the lubricant is momen­tarily trapped between slightly deformed op­posing surfaces.

elastomer rubber or rubber-like material, both natural and synthetic, used in making a wide variety of products, such as tires, seals, hose, belting, and footwear. In oil seals, an elastomer's chemical composition is a factor in determining its compatibility with a lubricant, particularly a synthetic lubricant. See natural rubber, synthetic rubber.


electrical discharge machining (EDM) - metalworking operation uti­lizing spark erosion for very precise shaping of the metal workpiece. The workpiece (anode) and electrical tool (electrode) are placed in a bath of dielectric fluid and brought closer together until the voltage overcomes the insulating effect of the fluid, causing a spark between the tool and workpiece. Consecutive discharges produce a series of micro-craters on the workpiece until the desired shape is achieved. See electrical discharge machining fluid, metalworking lubricant.


electrical discharge machining fluid - dielectric fluid, commonly pe­troleum based, used to bathe the metal workpiece during the machining process. The fluid must have high dielectric strength, high flash point, excellent oxidation stability, and low volatility. See electrical discharge machining, metalworking lubricant.


electrical insulating oil - high-quality oxidation-resistant oil refined to give long service as a dielectric and coolant for transformers and other electrical equipment. Its most common application is as a transformer oil. An insulating oil must resist the effects of elevated temperatures, electrical stress, and contact with air, which can lead to sludge formation and loss of insulation properties. It must be kept dry, as water is detrimental to dielectric strength. See gassing tendency, impulse strength, power factor.


electronic emission controls (EEC) - in automobiles, computerized engine operating controls that reduce automotive exhaust emissions of carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HC), primarily by optimizing combustion efficiency. This is accomplished by automatic monitoring and control of key engine functions and operating parameters, such as air-fuel ratio (see combustion), spark timing, and exhaust gas recirculation. See emissions (automotive), hydrocarbon emissions.


electrostatic ignition - See static electricity.


electrostatic precipitation - removal of particles suspended in a gas- as in a furnace flue - by electrostatic charging of the particles, and subsequent precipitation onto a collector in a strong electrical field. See emissions (stationary source), particulates, pollutants.


elemental analysis - See spectrographic analysis.


emission controls - see catalytic converter, emissions (automotive), emissions (stationary source), electronic emission controls, exhaust gas recirculation, positive crankcase ventilation.


emissions (automotive)-the three major pollutant emissions for which gasoline- powered vehicles are controlled are: unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). Diesel-pow­ered vehicles primarily emit NOx and particulates. Motor vehicles con­tribute only a small percentage of total man-made emissions of other atmospheric pollutant s, such as sulfur oxides. Evaporative HC emissions from the fuel tank and carburetor are adsorbed by activated carbon contained in a canister installed on the vehicle. Blow-by HC emissions from the crankcase are controlled by positive crankcase ventilation (PCV). Exhaust emissions of HC, CO, and NOx - the products of incomplete combustion - are controlled primarily by a catalytic con­verter, in conjunction with exhaust gas recirculation and increasingly sophisticated technology for improving combustion efficiency, including electronic emission controls. See emissions (stationary source), hydro­ carbon emissions, pollutants.


emissions (stationary source) - atmospheric pollutants from fossil fuel combustion in furnaces and boilers. Stationary combustion sources con­ tribute significantly to total man-made emissions of sulfur oxides - predominantly sulfur dioxide (S0 2), with some sulfur trioxide (S03) - nitrogen oxides (NOx), and particulates, but emit comparatively minor amounts of carbon monoxide (CO) and hydrocarbons (HC). There are several ways to control stationary source emissions. One method is flue gas scrubbing with a chemical like sodium hydroxide to remove sulfur. Another method involves burning naturally low-sulfur fuels. Lowering combustion temperatures helps reduce NOx formation. Lastly, you can use electrostatic precipitation to reduce particulate emissions. See emissions (automotive), pollutants.


emulsifiable (soluble) oil - See cutting fluid.


emulsified anionic asphalt (anionic emulsified asphalt) - emulsified asphalt in which the asphalt globules are electronegatively charged. There are common grades of anionic asphalt. One is RS asphalt, which is anionic rapid setting emulsified asphalt. Another is MS asphalt, an anionic medium setting emulsified asphalt. Lastly, there is SS asphalt, an anionic slow-setting emulsified asphalt.


emulsified cationic asphalt - emulsified asphalt in which the asphalt globules are electro-positively charged. Common grades of cationic emulsified asphalt are CRS asphalt - cationic rapid-setting emulsified asphalt; CMS asphalt - cationic me­dium-setting emulsified asphalt; CSS asphalt - cationic slow-setting emulsified asphalt. Emulsified cationic asphalt is superior to emulsified anionic asphalt in its ability to mix with wet stones, or aggregate, because its electro-positive charge aids in rapidly replacing the water adhering to the stones.

emulsifier - additive that promotes the formation of a stable mixture, or emulsion, of oil and water. Common emulsifiers are metallic soaps, certain animal and vegetable oils, and various polar compounds (having molecules that are water-soluble at one extremity of their structures and oil-soluble at the other).

emulsion - intimate mixture of oil and water, gene rally of a milky or cloudy appearance. Emulsions may be of two types: oil-in-water (where water is the continuo us phase) and water-in-oil (where water is the discontinuous phase). Oil-in-water emu ls ions are used as cutting fluids because of the need for the cooling effect of the water. Water-in-oil emulsions are used where the oil, not the water, must contact a surface- as in rust preventives, non-flammable hydraulic fluids, and compounded steam cylinder oils (see compounded oil); such emulsions are sometimes referred to as inverse emulsions. Emulsions are produced by adding an emulsifier. Emulsibility is not a desirable characteristic in certain lubricat­ing oils, such as crankcase or turbine oils, that must separate from water readily. Unwanted emulsification can occur as a result of oxidation products - which are usually polar compounds- or other contaminants in the oil. See illustration of an oil-in- water emulsion at polar compound. See air entrainment foaming, micro-emulsion.


emulsion flux asphalt - asphalt that can be blended with water and emulsifying chemicals for application at cooler temperatures than hot-mix asphalt; used in seal coating and road resurfacing.

energy - the capacity to do work. There are many forms of energy, any of which can be converted into any other form of energy. To produce electrical power in a steam turbine-generator system, the chemical energy in coal is converted in heat energy, which (through steam) is converted to the mechanical energy of the turbine, and in turn, converted into electrical energy. Electrical energy may then be converted into the mechanical energy of a vacuum cleaner, the radiant and heat energy of a light bulb, the chemical energy of a charged battery, etc. Conversion from one form of energy to another results in some energy being lost in the process (usually as heat). There are two kinds of mechanical energy: kinetic energy, imparted by virtue of a body's motion, and potential energy, impacted by virtue of a body's position (e.g., a coiled spring, or a stone on the edge of a cliff). Solar (radiant) energy is the basis of all life through the process of photosynthesis, by which green plants convert solar energy into chemical energy. Nuclear energy is the result of the conversion of a small amount of the mass of an unstable (radioactive) atom into energy. The fundamental unit of energy in the Systeme International is the joule. It can be expressed in other energy units, such as the calorie, British thermal unit (Btu), kilowatt-hour, etc., by use of appropriate conversion factors.

energy conservation - employment of less energy to accomplish the same amount of useful work; also, the reduction or elimination of any energy-consuming activity. Energy conservation is a vital goal in U.S. and world efforts to adjust to the declining availability of conventional oil and gas resources. Conservation will extend the time available to make the transition to alternative energy sources, such as solar energy and synthetic oil and gas, and will also reduce the economic hard ship imposed by rising energy prices.

Energy Conserving/Energy Conserving II - engine oil categories developed by SAE, ASTM, and AP! based on an oil's fuel- saving perfor­mance in passenger cars, vans, and light trucks. An "Energy Conserving" oil must produce a fuel economy improvement of 1.5% or greater over a reference oil in a standard ASTM test procedure. An "Energy Conserving II" oil must produce a fuel economy improvement of at least 2.7%. In actual vehicle operation, the fuel economy obtained by these lubricants may differ, depending on vehicle type, operating conditions, and driving habits. See fuel-economy oil.


engine deposits - hard or persistent accumulations of sludge, varnish, and carbonaceous residues due to blow-by of unburned and partially burned (partially oxidized) fuel, and/or from partial breakdown of the crankcase lubricant. Water from condensation of combustion products, carbon, residues from fuel or lubricating oil additives, dust, and metal particles also contribute. Engine deposits can impair engine performance and damage engine components by causing valve and ring sticking, clogging of the oil screen and oil passages, and excessive wear of pistons and cylinders. Engine deposits are increased by short trips in cold weather, high-temperature operation, heavy loads (such as pulling a trailer), and over­ extended oil drain intervals. See fuel injection.


engine oil (crankcase oil, motor oil) - oil carried in the crankcase, sump, or oil pan of a reciprocating internal combustion en­gine to lubricate all major engine parts; also used in reciprocating compres­sors and in steam engines of crankcase design. In automotive applications, it is the function of the engine oil not only to lu­bricate, but to cool hot engine parts, keep the en­gine free of rust and de­posits (see engine depos­its), and seal the rings and valves against leakage of combustion gases. Addi­tives in the oil greatly en­hance its ability to pre­vent excessive wear and deposit buildup, and they increase its resistance to oxidation and deteriora­tion at high temperatures. Additive content in a single viscosity grade oil is typically around 10 mass percent, and in a multi-grade oil, 15-20 percent. See Energy Conserving, AP! Engine Service Categories, military specifications for engine oils, SAE engine oil viscosity classification.


Engler viscosity - method for determining the viscosity of petroleum products; it is widely used in Europe, but has limited use in the U.S. The test method is similar to Saybolt Universal viscosity; viscosity values are reported as "Engler degrees."

enhanced recovery - in crude oil production, any method used to produce the oil remaining in a reservoir that has largely been depleted. See secondary recovery, tertiary recovery, reservoir.


entrainment - See air entrainment.


Environmental Protection Agency- see EPA.


EPA (Environmental Protection Agency) - agency of the federal executive branch, established in 1970 to control pollution through monitoring, regulation, and enforcement, and to coordinate and support environmental research.

EP additive - lubricant additive that prevents sliding metal surfaces from seizing und er conditions of extreme pressure (EP). At the high local temperatures associated with metal-to-metal contact, an EP additive combines chemically with the metal to form a surface film that prevents the welding of opposing asperities, and the consequent scoring that is destructive to sliding surfaces under high loads. Reactive compounds of sulfur, chlorine, or phosphorus are used to form these inorganic films.

EPDM rubber - see ethylene-propylene rubber.


EP oil - lubricating oil formulated to withstand extreme pressure (EP) operating conditions. See EP additive.


ester - chemical compound formed by the reaction of an organic or inorganic acid with an alcohol or with another organic compound contain­ing the hydroxyl (-OH) radical. The reaction involves replacement of the hydrogen of the acid with a hydrocarbon group. The name of an ester indicates its derivation, e.g., the ester resulting from the reaction of ethyl alcohol and acetic acid is called ethyl acetate. Esters have important uses in the formulation of some petroleum additives and synthetic lubricants. See dibasic acid ester, petroleum, phosphate ester.


ethane - gaseous paraffinic hydrocarbon(C2H6) present in natural gas and petroleum; used as a fuel, and as a feed stock in petrochemical manufacture. See distillation, hydrocarbon.

ethanol - also known as ethyl alcohol. Obtained principally from the fermentation of grains or blackstrap molasses; also obtained from ethylene, by absorption in sulfuric acid and hydrolyzing with water. Widely used as an industrial solvent, extraction medium, chemical inter­mediate, and in many proprietary products. One of several oxygen­ates that may be added to motor gasoline to reduce harmful automobile exhaust emissions. See gasohol.


ethylene - flammable gas (C2H4) derived from natural gas and petro­leum; the lowest molecular weight member of the generic family of olefins. Ethylene is widely used a feedstock in the manufacture of petro­chemicals, including polyethylene and other plastics.

ethylene-propylene rubber (EPM and EPDM) synthetic rubber: EPM is a polymer of ethylene and propylene; EPDM is a polymer of ethylene and propylene with a small amount of a third monomer (usually a diolefin) to permit vulcanization with sulfur. EPM and EPDM possess excellent resistance to ozone, sun light, and weathering, have good flex­ibility at low temperatures, and good electrical insulation properties. Used in the manufacture of tires, hoses, auto parts, coated fabrics, and electrical insulation.

evaporation - conversion of a liquid into a vapor; also, a test procedure that yields data on the volatility of a petroleum product. Evaporation testing of solvents may be performed in accordance with the Federation of Societies for Paint Technology Method II. A small sample of product is applied by hypodermic syringe to a filter paper on a sensitive spring balance. It's then allowed to evaporate under controlled conditions of temperature, relative humidity, air movement, etc. The loss of sample weight is plotted with respect to time. See distillation test.


exhaust gas recirculation (EGR) - system designed to reduce automo­tive exhaust emissions of nitrogen oxides (NOx). The system routes exhaust gases into the carburetor or intake manifold; the gases dilute the air-fuel mixture (see combustion) which lowers peak combustion tem­peratures, thus reducing the tendency for NOx to form. See emissions (automotive).


explosive limits (flammability limits) - upper and lower limits of petroleum vapor concentration in air outside of which combustion will not occur. As a general rule, below one volume percent concentration in air (lower explosive limit) the mixture is too lean to support combustion; above six volume percent (upper explosive limit), the mixture is too rich to burn.

extender - material added to a formulation to improve quality and process ability, or to reduce costs by substituting for a more expensive material (e.g., a low-cost solvent partially replacing a higher-cost solvent; a petroleum oil added to a rubber formulation).

extraction - use of a solvent to remove edible and commercial oils from seeds (e.g., soybeans), or oils and fats from meat scraps; also, the removal of reactive components from lube distillates (see solvent extraction) or other refinery process streams.


extreme pressure (EP) additive - see EP additive.



(Fahrenheit) - see temperature scales.


Falex test - a method for determining the extreme­ pressure (EP) or anti -wear properties of oils and greases. V blocks (with a large "V"­ shaped notch) are placed on opposite sides of a rotating steel shaft, and the apparatus is immersed in a bath of the test lubricant. Load is automatically increased until sei­zure occurs. Measurable wear scars are formed on the blocks. See EP additive.


false brinelling - see fretting.


fatty acid - any monobasic (one displaceable hydrogen atom per molecule) organic acid having the general formula CnH2n+1 COOH. Fatty acids derived from natural fats and oils are used to make soaps used in the manufacture of greases and other lubricants.

fatty oil - organic oil of animal or vegetable origin; can be added to petroleum oils to increase load-carrying ability, or oiliness. See com­ pounded oil, oiliness agent, saponification number.


FDA (Food and Drug Administration) - an agency that falls under the U.S. Department of Health and Human Services. It was established "to enforce the Federal Food, Drug, and Cosmetic Act, which was enacted by Congress. The Act's main purpose is to ensure foods are safe, pure, and wholesome, made under sanitary conditions. Drugs and therapeutic devices are safe and effective for their intended uses. Cosmetics are safe and prepared from appropriate ingredients; and all these products are honestly and informatively labeled and packaged."

feedstock - any material to be processed, e.g., gas oil for cracking, ethylene for petrochemical manufacture.

ferrography - particle analysis using precision magnets to strip iron­ laden and other susceptible particles from a used lube oil for study; results indicate extent of equipment wear and likelihood of imminent failure. Direct reading ferrography uses optical sensors to measure the density of particles collected and the ratio of large particles to small (fatigue­ related catastrophic failure generally is characterized by generation of particles larger than 10-15 microns). Analytical ferrography employs microscopic and photographic evaluation of wear particles. The test provides in-depth analysis of particle makeup (e.g., steel, copper, bronze) and type of wear (e.g., corrosion, metal -to-metal contact). See chromatog­raph, clay/ silica gel analysis, infrared analysis, mass spectrometer, particle count, spectrographic analysis.


FIA analysis - see fluorescent indicator adsorption.


fiber - in grease, form in which soap thickeners occur. On the average, soap fibers are about 20 times as long as they are thick; most are microscopic, so that the grease appears smooth.

fiber lubricant - an oil containing emulsifiers and anti-static agents, applied to synthetic fibers to lubricate them during processing into yarn; also called spin finish. See coning oil.


fifth wheel - large flat disk between a truck and trailer that permits the trailer to pivot from side to side. A fifth wheel is particularly subject to fretting, which is the removal of finely divided metal particles from rubbing surfaces due to oscillation, sliding or vibration. A grease formulated with mo­lybdenum disulfide can help control this type of wear.

film strength - see lubric­ity.


film temperature - see bulk temperature.


final boiling point - see distillation test.


fingerprint neutralizer polar compound in some rust preventives that places a barrier between the metal surface and perspiration deposited during handling of metal parts. In this way, corrosive activity of the salts and acids in perspiration is suppressed.

fire point- temperature at which the vapor concentration of a combustible liquid is sufficient to sustain combustion, as determined by test method ASTM D92, Cleveland Open Cup. See flash point.


fire-resistant fluid - lubricant used especially in high-temperature or hazardous hydraulic applications, such as steel mills and underground mining. Three common types of fire-resistant fluids exist. First, water-petroleum oil emulsions where water prevents petroleum burning. Second, water-glycol fluids. Lastly, non-aqueous fluids with low volatility, such as phosphate esters, silicones, and halogenated hydrocarbon-type fluids. See fire-resistant grease, flame propa­gation, synthetic lubricant.


fire-resistant grease grease formulated with special flame-retardant additives. Unlike a fire-resistant fluid, which will not readily ignite, afire­ resistant grease may burn but will rapidly extinguish itself after the ignition source has been removed.

flame propagation - self-sustaining burning of fuel after heat of combustion has been reached. Many fire-resistant hydraulic fluids - though they can be made to bum if subjected to sufficiently intense heat- do not generate sufficient heat of combustion of themselves to continue burning once the external source of heat is removed. See fire resistant fluids.


flammability limits - see explosive limits.


flammable liquid - a liquid having a closed cup flash point of not more than 60.5°C (141°F), as universally defined by the U.S. Department of Transportation (DOD, the International Civil Air Organization (ICAO), and the International Maritime Organization (IMO). ICAO and IMO expand the definition by including liquids with an open cup flash point of not more than 65.6°C (150 °F). DOT's hazardous material regulations have refinements that apply to domestic transportation only: 1) a combus­tible liquid is defined as a liquid having a closed cup flash point above 60.5°C (141°F) and below 93°C (200°F). 2) a "flammable liquid" with a flash point at or above 38°C (100°F) that does not meet the definition of any other hazard class may be reclassified as a "combustible liquid" for transportation over land; this provision does not apply to shipment by sea or air. 3) Materials classified as "combustible liquids" that are shipped in packages of 119 gallons or less are exempt from the domestic regulations if they are not subject to classification under any other hazard class. 4) Any material in a liquid phase with a flash point at or above 38°C (100°F) that is intention ally heated and transport ed at or above its flash point is classed as a "flammable liquid " when transported in bulk packaging. Addition­ ally, any material in a liquid phase that is offered for transportation at or above 100°C (212°F) is classified and regulated as an elevated tempera­ture material. See closed cup, open cup.


flash point - lowest temperature at which the vapor of a combustible liquid can be made to ignite momentarily in air, as distinct from fire point. Flash point is an important indicator of the fire and explosion hazards associated with a petroleum product. There are several ASTM tests for flash point, e.g., Cleveland open cup, Pensky-Martens closed tester, Tag closed tester, Tag open cup. See illustration, next column.

flexible coupling - connector designed to accommodate misalignment between two rotating power transmission shafts. Flexible couplings minimize noise and vibration and prevent excessive bearing loads. Some types of flexible couplings use metallic or rubber diaphragms that require no lubrication. Of the kind that require lubrication, there are two principal types: grid type and gear type. The grid-type flexible cou­pling consists of grooved hubs at­tached to the shaft ends and con­nected to each other by a spring­ steel grid that fits in to grooves around the circumference of each hub. The grid flexes and absorbs shock that might otherwise be trans­mitted from one shaft to another. A fairly stiff grease can be used because the movement of the grid against the grooves serves to keep the lubricant well-distributed. A gear-type flexible coupling consists of geared hubs fitted to the shaft ends and connected to each other by means of a sleeve with internal gear teeth that engage the teeth of the hubs. The hubs rock back and forth within the sleeve to accommodate angular misalignment. Gear-type couplings depend on centrifugal force to distribute the lubricant and thus require a relatively soft grease with good migrating properties. Certain gear-type couplings can be oil­ lubricated.

flexography - see printing processes.


Flow point - temperature at which waxy materials in a lubricating oil separate from a mixture of oil and Freon* R-12 refrigerant, giving a cloudy appearance to the mixture; also called Freon floc point. Generally used to evaluate the tendency of refrigeration oils to plug expansion valves or capillaries in refrigerant systems. Not to be confused with cloud point, the temperature at which wax precipitates from an undiluted oil.

fluid friction - see friction.


fluidizer - high boiling-point, the1m ally stable organic liquid used as an additive in gasoline to reduce deposits on the undersides of intake valves; also called solvent oil. See engine deposits.


fluorescent indicator adsorption (FIA) - method of measuring the relative concentration of saturated hydrocarbons, aromatics, and olefins in a petroleum product (usually a solvent or light distillate), as determined by test method ASTM D1319. The sample is passed through a column where it reacts with three dyes, each sensitive to one of the components. The relative concentration of the component is indicated by the length of the respective dyed zoned, viewed under ultraviolet light, which brings out the coloration of the dyes.

flux (flux oil) - a relatively non- volatile fraction of petroleum used as a diluent to soften asphalt to a desired consistency; also, a base stock for the manufacture of roofing asphalts.

foaming - occurrence of frothy mixture of air and a petroleum product (e.g., lubricant fuel oil) that can reduce the effectiveness of the product, and cause sluggish hydraulic operation, air binding of oil pumps, and overflow of tanks or sumps. Foaming can result from excessive agitation, improper fluid levels, air leaks, cavitation, or contamination with water or other foreign materials. Foaming can be inhibited with an anti-foam agent. The foaming characteristics of a lubricating oil can be determined by blowing air through a sample at a specified temperature and measuring the volume of foam, as described in test method ASTM D892. See air entrainment, emulsion.


fogging oil - light mineral seal oil injected in small quantities into a gas transmission line to settle dust or to seal joints by soaking the fiber or gasket materials. Also, oil used to generate smoke or fog to obscure visibility, or as a carrier for insecticides applied to large outdoor areas.

follower plate - heavy disc in a grease container which rests on the surface of the grease and assists its downward movement toward a dispensing pump inlet located at the bottom of the container.

food additive - non-nutritional substance added directly or in directly to food during processing or packaging. Petroleum food additives are usually refined waxes or white oils that meet applicable FDA standards. Applications of these substances are diverse. They serve as direct additives, coating fresh fruits and vegetables. Also, they act as indirect additives like impregnating oils for fruit and vegetable wrappers. They are dough divider oils, and defoamers for yeast and beet sugar production. They offer release and polishing functions in confectionery manufacturing. Finally, they act as rust preventives for meat processing equipment. See H-1/H -2 lubri­cants.


Food and Drug Administration - see FDA.


force-feed lubrication - any method in which pressure is applied to a lubricant in order to move it to the lubricated parts, e.g., a pump in a circulating lubrication system, a screw-down cap or plunger on a grease cup.


form oil - see concrete form coating.


fossil fuel - any fuel, such as crude oil and coal, derived from remains of ancient organisms that have been transformed over the ages by heat, pressure, and chemical action.

four-ball method - either of two lubricant test procedures, the Four-Ball Wear Method (ASTM D2266) and Four Ball EP (extreme pressure) Method (ASTM D2596), based on the same principle. Three steel balls are clamped together to form a cradle upon which a fourth ball rotates on a vertical axis. The balls are immersed in the lubricant under investigation. The Four Ball Wear Method is used to determine the anti-wear proper­ ties of lubricants operating under boundary lubrication conditions. The test is carried out at a specified speed, tempera­ture and load. At the end of a specified test time, the average diameter of the wear scars on the three lower balls is reported. The Four -Ball EP Method is designed to evaluate performance under much higher unit loads. The loading is in­creased at specified intervals until the rotating ball seizes and welds to the other balls. At the end of each interval the average scar diameter is recorded. Two values are generally reported - load wear index (formerly mean Hertz load) and weld point.


four -square gear oil tester - device consisting of two automotive drive­ axle systems to test the load-carrying capacity of hypoid gear (see gear) lubricants.

four-stroke-cycle - see internal combustion engine.


fraction, fractionation - see cut, distillation.


freezing point - a specific temperature that can be defined in two ways, depending on the ASTM test used. In ASTM D1015, which measures the freezing point of high-purity petroleum products (such as nitration grade toluene), freezing point is the temperature at which a liquid solidifies. In ASTM D2386, which measures the freezing point of aviation fuel, freezing point is that temperature at which hydrocarbon crystals formed on cooling disappear when the temperature of the fuel is allowed to rise.

Freon floc point - see floc point.


fretting - a wear form that stems from small-amplitude oscillations or vibrations. These movements result in the removal of finely divided particles from rubbing surfaces. For example, this occurs in the vibrations imposed on an automobile's wheel bearings when transported by rail car. Another instance is on the fifth wheel on tractor trailers. When it comes to ferrous metals, wear particles oxidize into a reddish, abrasive iron oxide. This looks like rust or corrosion and is sometimes called fretting corrosion. Other terms for this phenomenon include false brinelling, referring to localized fretting in a bearing's rolling elements, and friction oxidation. Fretting can be controlled with lubricants containing molybdenum disulfide.


fretting corrosion - see fretting.


friction - resistance to the motion of one surface over another. The amount of friction is dependent on the smoothness of the contacting surfaces, as well as the force with which they are pressed together. Friction between unlubricated solid bodies is independent of speed and area. The coefficient of friction is obtained by dividing the force required to move one body over a horizontal surface at constant speed by the weight of the body, e.g., if a force of 4 kilograms is required to move a body weighing 10 kilograms, the coefficient of friction is 0.4. Coefficients of rolling friction (e.g., the motion of a tire or ball bearing) are much less than coefficients of sliding friction (back and forth motion over two flat surfaces). Sliding friction is thus more wasteful of energy and can cause more wear. Fluid friction occurs between the molecules of a gas or liquid in motion and is expressed as shear stress. Unlike solid friction, fluid friction varies with speed and area. In general, lubrication is the substitution of low fluid friction in place of high solid-to-solid friction. See asperities, tribology.


friction oxidation - see fretting.


front-end volatility - see distillation test.


fuel economy oil engine oil specially formulated to increase fuel efficiency. A fuel economy oil works by reducing the friction between moving engine parts that waste fully consumes fuel energy. There are two known means of accomplishing this goal: 1) by reducing the viscosity of the oil to decrease fluid friction and 2) by using friction reducing additives in the oil to prevent metal-to-metal contact, or rubbing friction, between surface asperities.


fuel injection -method of introducing fuel into the combustion process as a finely divided spray under pressure through a small nozzle. Fuel injection is essential to the compression - ignition process of the diesel cycle. In most of the newer-model gasoline-powered cars fuel injec­tion has replaced carburation, largely due to EPA exhaust emission standards: fuel injection improves combustion efficiency, resulting in lower emissions. The location and design of fuel injectors is somewhat different between diesel and gasoline engines. In the diesel engine fuel is injected directly into the cylinder or the pre-combustion chamber. Since the injector nozzle intrudes into the cylinder it must be durable and relatively insensitive to deposit formation in the injector passages. In most gasoline engines, the fuel is injected into the intake manifold leading to the cylinder, either by a single throttle-body injector or by multiple port injectors (one for each cylinder). Gasoline engine port injectors are highly deposit sensitive, due to their extremely narrow passage clearances of only two-thousandths of an inch and their proximity to high combustion temperatures. This deposit sensitivity required gasoline suppli­ers to develop a new gen­eration of gasoline addi­tives that could keep these passages deposit-free. Diesel engine manufacturers have begun to express in­terest in diesel fuel addi­tives that can reduce de­ posits, thereby increasing combustion efficiency and improving emissions con­trol. Fuel injection has several advantages over carburation. It ensures more precise fuel metering in the cylinders, leading to improved combustion. It also guarantees more positive fuel delivery to the cylinder. This results in easier starts and faster acceleration. Another advantage is higher power output due to improved volumetric efficiency. Lastly, fuel injection leads to a reduction in exhaust emissions. See carburetor, emissions (automotive), engine deposits, internal combustion engine.

fuel oil - term encompassing a broad range of distillate and residual fuels identified by ASTM grades. Grade No. 1, a kerosene-type fuel, is a light distillate fuel that has the lowest boiling range. No. 2 fuel oil, popularly called heating oil, has a higher boiling range and is commonly used in home heating. It is comparable in boiling range to diesel fuel. Grades 4, 5, and 6 are called heavy fuel oils (HFO), or residual fuel oils; they are composed largely of heavy pipe still bottoms. Because of their high viscosity, No. and No. 6 fuel oils require preheating to facilitate pumping and burning. No. 6 fuel oil is also called Bunker C fuel oil. See distillation.


fuel pump - mechanism for delivering fuel from the tank to the carburetor or fuel injection system of a gasoline engine, to the fuel injectors of a diesel engine, or to the fuel atomizers of an oil- fired boiler.

full-fluid-film lubrication - presence of a continuous lubricating film sufficient to completely separate two surfaces, as distinct from boundary lubrication. Full-fluid-film lubrication is nor­mally hydrodynamic lu­brication, whereby the oil adheres to the moving part and is drawn into the area between the sliding sur­faces, where it forms a pressure, or hydrody­namic wedge. See ZN/P curve. A less common form of full-fluid-lubrica­tion is hydrostatic lubri­cation, wherein the oil is supplied to the bearing area under sufficient external pressure to separate the sliding surfaces.

fully refined wax - see refined wax.


fungible product - commodity product, typically a fuel, that is inter­ changeable with comparable competitive products; fungible fuels made by different manufacturers can be shipped together through a common pipeline. Fuels containing proprietary additives are not fungible. See proprietary product.


furfural - colorless liquid, C4H30 CHO, employed in petroleum refin­ing as a solvent to extract mercaptans, polar compounds, aromatics, and other impurities from oils and waxes. Also used in the manufacture of dyes and plastics.

Furol viscosity - viscosity of a petroleum oil measured with a Saybolt Furol viscometer; see viscosity.


FZG four-square gear oil test - test used in developing industrial gear lubricants to meet equipment manufacturers' specifications. The FZG test equipment consists of two gear sets, arranged in a four-square configura­tion, driven by an electric motor. The test gear set is run in the lubricant at gradually increased load stages until failure, which is the point at which a 10 milli gram weight loss by the gear set is recorded. Also called Niemann four-square gear oil test.


gas blanket - atmosphere of inert gas (usually nitrogen) lying above a lubricant in a tank and preventing contact with air. In the absence of such a covering, the lubricant would be subject to oxidation. Gas blankets are commonly used with heat transfer fluids and electrical insulating oils.


Gas Bubble Separation Time of Petroleum Oils – the number of minutes needed for gas entrained in a steam turbine oil to reduce in volume to 0.2%, under the conditions of ASTM D3427. Compressed gas is blown through the test oil, which has been heated to a temperature of 25, 50, or 75°C; measurement begins after the gas flow is stopped. See air entrainment.


gas chromatography - see chromatography.


gas engine internal combustion engine, either two or four-stroke cycle, powered by natural gas or LPG. Commonly used to drive compres­sors on gas pipelines, utilizing as fuel a portion of the gas being com­pressed. Gas engine combustion chamber temperatures are typically hotter than in gasoline or diesel engines and thus have a greater tendency toward nitration (formation of nitrogen oxides, which can degrade the crankcase oil) and piston deposits (which can impair engine performance and damage engine parts.) Gas engine oils are specially formulated to control these tendencies. See engine deposits.


gasohol - blend of 10 volume percent anhydrous ethanol (ethyl alcohol) and 90 volume percent unleaded gasoline.


gas oil - liquid petroleum distillate, higher boiling than naphtha; initial boiling point may be as low as 204°C (400°F). Gas oil is called light or heavy, depending on its final boiling point. It is used in blending fuel oil and as refinery feedstock in cracking operations. See distillation.


gasoline (automotive) - blend of light hydrocarbon fractions of rela­tively high anti-knock value. Automotive, or motor, gasoline may consist of the following components: straight-run naphthas, obtained by the primary distillation of crude oil; natural gasoline, which is "stripped", or condensed, out of natural gas; cracked naphthas; reformed naphthas; and alkylate. (See alkylation, catalytic cracking, reforming). A high-quality gasoline has the following properties. (1) proper volatility to ensure easy starting and rapid warm-up. (2) clean-burning characteristics to minimize harmful combustion chamber deposits. (3) additives to prevent rust, oxidation, and deposits in carburetors, intake valves and fuel injectors. (4) sufficiently high-octane number to prevent engine knock. See aviation gasoline.


gassing tendency - measure of an electrical insulating oil's ability to absorb hydrogen under electrical stress, as determined by ASTM D2300. An oil that evolves hydrogen has a positive gassing tendency, which is undesirable, since hydrogen can be hazardous under certain conditions.

gas turbine - see internal combustion engine, turbine.


gauge pressure - see pressure.


G.C. - gas chromatography.


gear - machine part which transmits motion and force from one rotary shaft to another by means of successively engaging project ions, called teeth. The smaller gear of a pair is called the pinion; the larger, the gear. When the pinion is on the driving shaft, the gear set acts as a speed reducer; when the gear drives, the set acts as a speed multiplier. The basic gear type is the spur gear, or straight-tooth gear, with teeth cut parallel to the gear axis. Spur gears transmit power in applications utilizing parallel shafts. In this type of gear, the teeth mesh along their full length, creating a sud­den shift in load from one tooth to the next, with consequent noise and vibration. This problem is overcome by the helical gear, which has teeth cut at an angle to the center of rotation, so that the load is transferred progressively along the length of the tooth from one edge of the gear to the other. When the shafts are not parallel, the most common gear type used is the bevel gear, with teeth cut on a sloping gear face, rather than parallel to the shaft. The spiral bevel gear has teeth cut at an angle to the plane of rotation, which, like the helical gear, reduces vibration and noise. A hypoid gear resembles a spiral bevel gear, except that the pinion is offset so that its axis does not intersect the gear axis; it is widely used in automobiles between the engine drives haft and the rear axle. Offset of the axes of hypoid gears introduces additional sliding bet ween the teeth, which, when combined with high loads, requires a high­ quality EP oil. A worm gear consists of a spirally grooved screw moving against a toothed wheel; in this type of gear, where the load is transmitted across sliding, rather than rolling, surfaces, compounded oils or EP oils are usually necessary to maintain effective lubrication.

gear box housing - casing for gear sets that transmit power from one rotating shaft to another. A gear box has several functions: it is precisely bored to control gear and shaft alignment, it contains the gear oil, and it protects the gears and lubricant from water, dust, and other environmental contaminants. Gear boxes are used in a wide range of industrial, automotive, and home machinery, e.g., paper mills, automotive transmissions, electric mixers. Not all gears are enclosed in gear boxes; some are open to the environment and are commonly lubricated by highly adhesive greases. See open gear.


gear oil (automotive) - long- life oil of relatively high viscosity for the lubrication of rear axles and some manual transmissions. Most final drives and many accessories in agricultural and construction equipment also require gear oils. Straight (non-additive) mineral gear oils are suitable for most hypoid rear axles (see gear) and for some manual transmissions. Use of such oils is declining, however, in favor of EP (extreme pressure) gear oils (see EP oil) suitable both for hypoid gears (see gear) and for all straight mineral oil applications.

gear oil (industrial) - high quality with good oxidation stability, rust protection, and resistance to foaming, for service in gear housings and enclosed chain drives. A turbine oil or R&O oil is the usual gear oil recommendation for non-shock loaded reducers. Specially formulated industrial EP gear oils (see EP oil) are used where highly loaded gear sets or excessive sliding action (as in worm gears) is encountered. See gear, gear box.


gear shield - highly adhesive lubricant of heavy consistency, formulated with asphaltic compounds or polymers for protect ion of exposed gears and wire rope in circumstances where the lubricant cannot readily be replenished. Many gear shield lubricants must be softened with heat or cut back with solvents before they can be applied. See open gear, solvent­ cutback.


gear-type coupling – see flexible coupling.


general purpose oils - see once-through lubrication.


generation 5 lubricant - an LMOA-approved locomotive crankcase oil that meets critical OEM oxidation corrosion, and friction tests and that has been successfully field tested in accordance with LMOA procedures, including 100,000 miles of operation and 180-day minimum drain inter­vals.


gilsonite - a naturally occurring asphalt mined from rock fissures. It is hard and brittle and has a high melting point. It is used in the manufacture of rust preventives, paints, sealants, and lacquers.

gloss - property of wax determinable by measuring light reflected from a wax-treated paper surface. Gloss stability is evaluated after a sample of treated paper has been held at an elevated temperature for a specified period.

gram calorie - see calorie.


graphite - a soft form of elemental carbon, gray to black, in color. It occurs naturally or is synthesized from coal or other carbon sources. It is used in the manufacture of paints, lead pencils, crucibles, and electrodes, and is also widely used as a lubricant, either alone or added to conventional lubricants.

gravure - see printing processes.


grease - mixture of a fluid lubricant (usually a petroleum oil) and a thickener (usually a soap) dispersed in the oil. Because greases do not flow readily, they are used where extended lubrication is required and where oil would not be retained. The thickener may play as important a role as the oil in lubrication. Soap thickeners are formed by reacting (saponifying) a metallic hydroxide, or alkali, with a fat, fatty acid, or ester. The type of soap used depends on the grease properties desired. Calcium (lime) soap greases are highly resistant to water, but unstable at high temperatures. Sodium soap greases are stable at high temperatures but wash out in moist conditions. Lithium soap greases resist both heat and moisture. A mixed-base soap is a combination of soaps, offering some of the advan­tages of each type. A complex soap is formed by the reaction of an alkali with a high-molecular-weight fat or fatty acid to form a soap, and the simultaneous reaction of the alkali with a short-chain organic or inorganic acid to form a metallic salt (the complexing agent). Complexing agents usually increase the dropping point of grease. Lithium, calcium, and aluminum greases are common alkalis in complex-soap greases. Non­ soap thickeners, such as clays, silica gels, carbon black, and various synthetic organic materials are also used in grease manufacture. A multi­-purpose grease is designed to provide resistance to heat, as well as water, and may contain additives to increase load-carrying ability and inhibit rust. See block grease, bulk appearance, colloid, consistency (grease), fire-resistant grease, penetration (grease).


grease cup - grease applicator screwed into a tapped hole in a bearing; grease is fed from the cup to the bearing either mechanically by means of a screw-down cap or plunger, or automatically by means of a spring­ loaded plunger. See grease gun.


grease gun - device for injecting pressurized grease into a bearing; the bearing receives the grease through a spring-loaded ball-check valve that lets the grease in but prevents it from running back out. A grease gun contains a reservoir for grease, a nozzle that fits tight against the fitting or clamps on to it, and a means for applying pressure to the grease. A grease gun has advantages over a grease cup: it can handle a harder grease, and the pressure can drive the fresh charge of grease into very tight clearances and flush out old grease that may have become contaminated with foreign matter. See high-pressure-injection injury.


grease gun injury - see high pressure injection injury.


grid-type coupling - see flexible coupling.


gum in gasoline - oily, viscous contaminant that may form, due to oxidation during storage. Gum formation in gasoline can cause serious fuel system problems, such as carburetor malfunctioning and intake valve sticking. The amount of gum in motor gasoline, aviation gasoline, and aircraft turbine fuel can be determined by evaporating a measured sample by means of air or steam flow at controlled temperature, and weighing the residue, as described in test method ASTM D381.


H-1/H-2 - lubricants-lubricants evaluated, approved, and listed by the U.S. Department of Agriculture (USDA) for use in federally inspected meat and poultry operations. USDA H-1 lubricants are approved for equipment where there may be incidental exposure to edible product USDA H-2 lubricants are approved for equipment where there is no possibility of the lubricated part or lubricant contacting edible product (e.g., a closed and sealed gear box). See food additive.


halogen - any of a group of five chemically related nonmetallic ele­ments: chlorine, bromine, fluorine, iodine, and astatine. Chlorine com­pounds are used as EP additives in certain lubricating oils, and as constituents of certain petrochemicals (e.g., vinyl chloride, chlorinated waxes). Chlorine and fluorine compounds are also used in some synthetic lubricants.


hazard - see health hazard.


Hazard Communication Standard - an OSHA regulation. It mandates that petroleum and chemical manufacturers evaluate their products' health and physical risks. Manufacturers and importers also need to communicate hazard information to customers and employees. This is done via Material Safety Data Sheets, or MSDSs. Besides MSDSs, product labels are used to share hazard information. Employees are trained to understand this data as well.

hazardous material - or dangerous goods internationally, concerns materials transportation. It's any shipped product that could harm people and property. This is according to definitions by the U.S. Department of Transportation, International Civil Aviation Organization, and the International Maritime Organization. These organizations publish strict procedures for packing, shipping, and hand ling hazardous materials. The definition encompasses explosives, flammable and high­ pressure gases, flammable liquids (including certain highly volatile petro­leum products such as fuels and solvents), corrosives, poisons, materials shipped at elevated temperatures, and environmental hazards.

health hazard - as defined by OSHA, "a chemical for which there is statistically significant evidence based on at least one study conducted in accordance with established scientific principles that acute or chronic health effects may occur in exposed employees." The term" health hazard" includes chemicals that are carcinogens; toxic or highly toxic agents; reproductive toxins; irritants; corrosives; sensitizers; liver, kidney, nerve, or blood toxins; and agents that damage the lungs, skin, eyes, or mucous membranes.

heating oil - see fuel oil.


heating value - see heat of combustion.


heat of combustion - measure of the available energy content of a fuel, under controlled conditions specified by test method ASTM D240 or D2382. Heat of combustion is determined by burning a small quantity of a fuel in an oxygen bomb calorimeter and measuring the heat absorbed by a specified quantity of water within the calorimeter. Heat of combust ion is expressed either as calories per gram or British thermal units per pound. Also called thermal value, heating value, calorific value.


heat-set inks - letterpress and lithographic inks that dry under the action of heat by evaporation of their high-boiling solvent. See printing ink, printing processes.


heat transfer fluid - circulating medium (often a petroleum oil) that absorbs heat in one part of a system (e.g., a solar heating system or a remote oil- fired system) and releases it to another part of the system. Heat transfer fluids require high resistance to cracking (molecular breakdown) when used in systems with fluid temperatures above 260°C (500°F). See bulk temperature. Systems can be either closed or open to the atmosphere. To prevent oxidation in a closed system an inert gas is sometimes used in the expansion tank (or reservoir) to exclude air (oxygen). See gas blanket. If the system is open and the fluid is exposed simultaneously to air and to temperatures above 66°C (150°F), the fluid must also have good oxidation stability, since a protective gas blanket cannot be contained.

heat transfer oil - see heat transfer fluid. heat treating oil - see quenching oil. heavy crude naphtha - see naphtha.


heavy-duty oil - an oil suitable for use in commercial diesel engine service. See API Service Categories.


heavy ends - highest boiling portion in a distilled petroleum fraction or finished product. In motor gasoline, the heavy ends do not fully volatilize until the engine has warmed. See light ends.


heavy fuel oil - see fuel oil.


helical gear - see gear.


heptane - liquid paraffinic hydrocarbon containing seven carbon atoms in the molecule, which may be straight-chain (normal) or branched-chain (iso). Heptane can replace hexane when a less volatile solvent is desired. This is useful in creating certain adhesives and lacquers. Heptane is also useful in extracting edible and commercial oils. It is mixed with isooctane to form a standard reference fuel. This blend is used in laboratory determinations of octane number.

hexane - highly volatile paraffinic hydrocarbon containing six carbon atoms in the molecule; it may also contain six-carbon isoparaffins. Widely used as a solvent in adhesive and rubber solvent formulations and in the extraction of a variety of edible and commercial oils. Normal hexane (a straight-chain six-carbon molecule) can cause peripheral polyneuropathy, a progressive and potentially irreversible disorder of the nervous system; it therefore must be handled with appropriate precautions.

high-pressure-injection injury - injury caused by the accidental injec­tion of grease or oil under pressure through the skin and into the underlying tissue; also called a grease gun injury. Such an injury requires immediate medical attention.

high-pressure normal phase liquid chromatography - see chroma­tography.


homogenization - intimate mixing of a lubricating grease or an emul­sion by intensive shearing action to obtain more uniform dispersion of the components.

horsepower - unit of power equal to 33,000 foot-pounds per minute, equivalent to 745.7 watts.

hot-dip rust preventive - petroleum-based rust preventive, consisting of a blend of oil, wax or asphalt, and rust-inhibiting additives, that must be melted before application.

humidity - water vapor in the atmosphere. Absolute humidity is the amount of water vapor in a given quantity of air; it is not a function of temperature. Relative humidity is a ratio of actual atmospheric moisture to the maximum amount of moisture that could be carried at a given temperature, assuming constant atmospheric pressure. The higher the temperature - other factors remaining constant - the lower the relative humidity (i.e., the drier the air).

hydrated soap grease thickener that has water incorporated into its structure to improve structural stability of the grease. See grease.


hydraulic fluid - fluid serving as the power transmission medium in a hydraulic system. The more commonly used fluids are petroleum oils, synthetic lubricants, oil-water emulsions, and water-glycol mixtures. Premium hydraulic fluid features several key requirements. Firstly, it must have the correct viscosity and high viscosity index. If necessary, it requires anti-wear protection. Good oxidation stability is also essential. Additionally, it needs an adequate pour point and good demulsibility. Rust inhibition, often via rust inhibitor, is also vital.

The fluid must resist foaming. Lastly, it should be compatible with seal materials. Anti-wear oils are frequently used in compact, high-pressure, and high­ capacity pumps that require extra lubrication protection. Certain synthetic lubricants and water-containing fluids are used where fire resistance is needed. Synthetic lubricants also are used in extreme temperature condi­tions. See fire-resistant fluid.


hydraulic system - system designed to transmit power through a liquid medium, permitting multiplication of force in accordance with Pascal's law, which states that "a pressure exerted on a confined liquid is transmit­ted undiminished in all directions and acts with equal force on all equal areas." Hydraulic systems have six basic components. (1) a reservoir to hold the fluid supply. (2) a fluid to transmit the power. (3) a pump to move the fluid. (4) a valve to regulate pressure. (5) a directional valve to control the flow. (6) a working component - such as a cylinder and piston or a shaft rotated by pressurized fluid. This turns hydraulic power into mechanical motion. Hydraulic systems offer several advantages over mechanical systems. They eliminate complicated mechanisms. For instance, cams, gears, and levers are less subject to wear. They are usually easily adjusted for control of speed and force. They are also adaptable to both rotary and linear transmission of power. They can transmit power over long distances and in any direction with small losses.

hydraulic transmission fluid - see automatic transmission fluid.


hydraulic turbine - see turbine.


hydrocarbon - chemical compound of hydrogen and carbon; also called an organic compound. Hydrogen and carbon atoms can be combined in virtually countless ways to make a diversity of products. Carbon atoms form the skeleton of the hydrocarbon molecule and may be arranged in chains (aliphatic) or rings (cyclic). There are three principal types of hydrocarbons that occur naturally in petroleum: paraffins, naphthenes, and aromatics, each with distinctive properties. Paraffins are aliphatic, the others cyclic. Paraffins and naphthenes are saturated; that is, they have a full complement of hydrogen atoms and, thus, only single bonds between carbon atoms. Aromatics are unsaturated and have as part of their molecular structure at least one benzene ring, i.e., six carbon atoms in a ring configuration with alternating single and double bonds. Because of these double bonds, aromatics are usually more reactive than paraffins and naphthenes, and are thus prime starting materials for chemical synthesis. Other types of hydrocarbons are formed during the petroleum refining process. Important among these are olefins and acetylenes. Olefins are unsaturated hydrocarbons with at least one double bond in the molecular structure, which may be in either an open chain or ring configuration; olefins are highly reactive. Acetylenes are also unsaturated and contain at least one triple bond in the molecule. See aliphatic hydrocarbon, satu­rated hydrocarbons, unsaturated hydrocarbons.


hydrocarbon (HC) emissions - substances considered to be atmo­spheric pollutants because the more reactive hydrocarbons (e.g., aromat­ics) undergo a photochemical reaction with nitrogen oxides (NOx) to form oxidants, components of smog that can cause eye irritation and respiratory problems. Motor vehicles account for about one-third of man-made hydrocarbon emissions, although automotive emission controls are reduc­ing this a mount. The greatest portion of total atmospheric hydrocarbons is from natural sources, such as pine trees. See catalytic converter, emissions (automotive), pollutants.


hydro-cracking - a refining process. Middle and heavy distillate fractions get broken into smaller molecules in the presence of hydrogen. This occurs under high pressure and moderate temperature. The result is high-octane gasoline, turbo fuel components, and middle distillates. These possess good flow characteristics and cetane ratings. The process is a combination of hydrogenation and crackingSee distillation.


hydro-sulfurization - refinery process in which sulfur is removed from petroleum streams by treating it with hydrogen to form hydrogen sulfide, which can be stripped from the oil as a gas.

hydrodewaxing - see dewaxing.


hydrodynamic lubrication - see full-fluid film lubrication.


Hydrofined - processed by a form of hydrogen treating in which refinery distillate, lube, and wax streams are treated with hydrogen at elevated temperatures and mode rate pressures in the presence of a catalyst, to improve color and stability and reduce sulfur content. See distillation.


hydro-forming - a dehydrogenation process in which naphthas are passed over a solid catalyst at elevated temperatures and moderate pressures in the presence of hydrogen to form high-octane motor gasoline, high-grade aviation gasoline, or aromatic solvents. The process is a net producer of hydrogen. See distillation.


hydrogenation - in refining, the chemical addition of hydrogen to a hydrocarbon in the presence of a catalyst; a severe form of hydrogen treating. Hydrogenation may be either destructive or non-destructive. In the former case, hydrocarbon chains are ruptured (cracked) and hydrogen is added where the breaks have occurred. In the latter, hydrogen is added to a molecule that is unsaturated (see unsaturated hydrocarbon) with respect to hydrogen. In either case, the resulting molecules are highly stable. Temperatures and pressures in the hydrogenation process are usually greater than in Hydrofining. See distillation.


hydrogen sulfide (H2S) - gaseous compound of sulfur and hydrogen commonly found in crude oil; it is extremely poisonous, corrosive, and foul-smelling. See mercaptan.


hydrogen treating- refining process in which hydrocarbons are treated with hydrogen in the presence of a catalyst at relatively low temperatures to remove mercaptans and other sulfur compounds and improve color and stability. See distillation.


hydrolytic stability-ability of additives and certain synthetic lubricants to resist chemical hydrolysis) in the presence of water.

hydrometer - see specific gravity.


hydrophilic - also hygroscopic, having an affinity for water. Some polar compounds are simultaneously hydrophilic and oil soluble.

hydrophobic - the opposite of hydrophilic.


hydrostatic lubrication - see full-fluid-film lubrication.


hygroscopic - see hydrophilic.


hypoid gear - see gear.



IBP - initial boiling point; see distillation test.


IFT - see interfacial tension.


immiscible - incapable of being mixed without separation of phases. Water and petroleum oil are immiscible under most conditions, although they can be made miscible with the addition of an emulsifier. See miscible.


impact odor - see bulk odor.


impulse strength - measure of an electrical insulating oil's resistance to transient voltage, such as that from lightning strikes or switching surges, expressed in terms of breakdown voltage as determined under ASTM D3300 impulse conditions.

induction period - the time in an oxidation test during which oxidation proceeds at a constant and relatively low rate. It ends at a point at which the rate of oxidation increases sharply.

industrial asphalt - oxidized asphalt used in the manufacture of roofing, asphaltic paints, mastics, and adhesives for laminating paper and foil. Industrial asphalt is generally harder than asphalt cement, which is used for paving.

industrial lubricant - any petroleum or synthetic - base fluid (see syn­thetic lubricant) or grease commonly used in lubricating industrial equip­ment, such as gears, turbines, and compressors.


infrared analysis - form of absorption spectroscopy that identifies or­ganic functional groups present in a used oil sample by measuring their infrared absorption at specific infrared wavelengths; absorbance is pro­portional to concentration. The test can indicate the presence of water, hydrocarbon contamination of a synthetic lubricant, oxidation, and nitration. Fourier Transforms Infrared (FTIR) permits the generation of complex curves from digitally repre­sented data. See chromatography. ferrography, mass spectrometer, par­ticle count, spectrographic analysis.


inhibitor - additive that improves the performance of a petroleum product through the control of undesirable chemical reactions. See corrosion inhibitor, oxidation inhibitor, rust inhibitor.


initial boiling point (IBP) - see distillation test.


ink - see printing ink.


ink oil - see printing ink solvent.


inkometer - see tack.


ink release agent - lubricant used to coat the inside of containers to facilitate the removal of ink varnishes, or flushes, which are introduced into the containers as liquids, but afterwards cool and harden.

inorganic compound - chemical compound, usually mineral, that does not include hydrocarbons and their derivatives. However, some relatively simple carbon compounds, such as carbon dioxide, metallic carbonates, and carbon disulfide are regarded as in organic compounds.

insoluble resins - see insolubles.


insolubles - test for contaminants in used lubricating oils, under condi­tions prescribed by test method ASTM D893. The oil is first diluted with pentane, causing the oil to lose its solvency for certain oxidation resins and causing the precipitation of such extraneous materials as dirt, soot, and wear metals. These contaminants are called pentane insolubles. The pentane insolubles may then be treated with toluene, which dissolves the oxidation resins (benzene was formerly used). The remaining solids are called toluene insolubles. The difference in weight between the pentane insolubles and the toluene insolubles is called insoluble resins. Testing for grease insolubles is described in ASTM D128.

insulating oil - see electrical insulating oil.


inter-cooling - cooling of a gas between pressurizing stages in a compres­sor. It permits reduced work in the compression phase because cooler gas is more easily compressed. After-cooling is the final cooling following the last compression stage.

interfacial tension (IFT) - the force required to rupture the interface between two liquid phases. The interfacial tension between water and a petroleum oil can be determined by measuring the force required to move a platinum ring upward through the interface, under conditions specified by test method ASTM D971. Since the interface can be weakened by oxidation products in the oil, this measurement may be evidence of oil deterioration. The lower the surf ace tension be low the original value, the greater the extent of oxidation. ASTM D971 is not widely used with additive-containing oils, since additives may affect surface tension, thus reducing the reliability of the test as an indicator of oxidation.

Internal combustion engine - heat engine driven directly by the expansion of combustion gases, rather than by an externally produced medium, such as steam. Basic forms of the internal combustion engine include several types. These consist of the gasoline engine and gas engine, both involving spark ignition. Furthermore, there's the diesel engine, associated with compression ignition. Lastly, the gas turbine involves continuous combustion. Diesel compression-ignition engines are more fuel-efficient than gasoline en­gines because compression ratios are higher, and because the absence of air throttling imp roves volumetric efficiency. Gasoline, gas (natural gas, propane), and diesel engines operate either on a four-stroke (Otto cycle) or a two-stroke cycle. Most gasoline engines are of the four-stroke type, with operation as follows. (1) intake - piston moves down the cylinder, drawing in a fuel-air mixture through the intake valve. (2) compression - all valves closed, piston moves up, compressing the fuel-air mixture, and spark ignites mixture near top of stroke. (3) power - rapid expansion of hot combustion gases drive piston down; all valves remain closed. (4) exhaust - exhaust valve opens, and piston returns, forcing out spent gases. The diesel four-stroke cycle differs in that only air is admitted on the intake stroke, fuel is injected at the top of the compression stroke, and the fuel-air mixture is ignited by the heat of compression rather than by an electric spark. The four-stroke cycle engine has certain advantages over a two-stroke, including higher piston speeds, wider variation in speed and load, cooler pistons, no fuel lost through the exhaust, and lower fuel consumption. The two-stroke cycle eliminates the intake and exhaust strokes of the four-stroke cycle. As the piston ascends, it compresses the charge in the cylinder, while simultaneously drawing a new fuel-air charge into the crankcase, which is air-tight. (In the diesel two-stroke cycle, only air is drawn in; the fuel is injected at the top of the compression stroke.) After ignition, the piston descends on the power stroke, simultaneously compressing the fresh charge in the crankcase. Toward the end of the power stroke, intake ports in the piston skirt admit a new fuel-air charge that sweeps exhaust products from the cylinder through exhaust ports; this means of flushing out exhaust gases is called " scavenging". Because the crankcase is needed to contain the intake charge, it cannot double as an oil reservoir. Therefore, lubrication is generally supplied by oil that is pre­mixed with the fuel. An important advantage of the two-stroke-cycle engine is that it offers twice as many power strokes per cycle and, thus, greater output for the same displacement and speed. Because two-stroke engines are light in relation to their output, they are frequently used where small engines are desirable, as in chain saws, outboard motors, and lawn mowers. Many commercial, industrial, and railroad diesel engines are also of the two- stroke type. Gas turbines differ from conventional internal combustion engines in that a continuous stream of hot gases is directed at the blades of a rotor. A compressor section supplies air to a combustion chamber into which fuel is sprayed, maintaining continuous combustion. The resulting hot gases expand through the turbine unit, turning the rotor and driveshaft. See fuel injection, turbine.


International Air Transport Association (IATA) - industry trade orga­nization, whose membership includes virtually all the world's air carriers. See Department of Transportation, International Civil Aviation Organi­zation, International Maritime Organization.


International Civil Aviation Organization (ICAO) - regulatory agency under the auspices of the United Nations Committee on Dangerous Goods; its responsibilities include regulation of air transport of hazardous mate­rial. The agency works closely with the International Air Transport Association (IATA) in developing air transport rules and data. See Department of Transportation, International Maritime Organization.

International Maritime Organization (IMO)-United Nations organi­zation that promulgates regulations affecting the carriage of dangerous goods by sea.

International System of Units - see SI.


inverse emulsion - see emulsion.

Ion - electrically charged atom, or group of atoms, that has lost or gained electrons. 

isomer - molecule having the same molecular formula as another molecule, but having a different structure and, therefore, different proper­ties. As the carbon atoms in a molecule increase, the number of possible combinations, or isomers, increases sharply. For example, octane, an 8-carbon-atom molecule, has 18 isomers; decane, a 10-carbon-atom mol­ecule, has 75 isomers.

isooctane - an isomer of octane (CsH Is) having very good antiknock properties. With a designated octane number of 100, isooctane is used as a standard for determining the octane number of gasolines.

isoparaffin branched isomer of a straight-chain paraffin molecule.

isoprene rubber - see polyisoprene rubber.


isothermal - pertaining to the conduct of a process or operation of equipment under conditions of constant temperature.

ISO viscosity classification system - international system, approved by the International Standards Organization (ISO), for classifying industrial lubricants according to viscosity. Each ISO viscosity grade number designation corresponds to the mid-point of a viscosity range expressed in centistokes (cSt) at 40°C. For example, a lubricant with an ISO grade of 32 has a viscosity within the range of 28.8 - 35.2 cSt, the mid-point of which is 32.


jet fuel - see turbo fuel.


joule - unit of energy in the Systeme International, equal to the work done when the point of application of a force of one newton is displaced a distance of one meter in the direction of the force.

journal - that part of a shaft or axle which rotates in or against a bearing.


Journal Bearing - A sliding type of bearing having either rotating or oscillatory motion and in conjunction with which a journal operates. In a full or sleeve type journal bearing, the bearing surface is 360 degrees in extent. In a partial bearing, the bearing surface is less than 360 degrees; 150, 120 degrees, etc.



Karl Fischer Method - method for determining water content (ppm or vol%) of liquid petroleum products and crude oil using the Karl Fischer equipment (ASTM D6304). See crackle test.


kauri-butanol (KB) value - a measure of the solvency of a hydrocar­bon; the higher the kauri-butanol value, the greater the general solvent power of the hydrocarbon. Under test conditions prescribed in test method ASTM D1133, a hydrocarbon sample is added to a standard solution of kauri gum in butyl alcohol (butanol) until sufficient kauri gum precipitates to blur vision of 10-point type viewed through the flask. When used in varnish, lacquer, and enamel formulations, a hydrocarbon diluent with a high kauri-butanol value dissolves relatively large quantities of solids.

Kelvin (°K) - see temperature scales.


kerosene - relatively colorless light distillate, heavier than gasoline (see distillation). It is used for lighting and heating, and as a fuel for some internal combustion engines. ASTM D3699 defines two kerosene grades. Grade 1-K is a low-sulfur kerosene with a maximum sulfur content of 0.04 mass percent. This grade is designed for use in fluteless burner appliances. Meanwhile, Grade 2-K comes with a maximum sulfur content of 0.30 mass percent. Grade 2-K is intended for use in flue-connected appliances.

ketone - any of a class of organic compounds having the general formula R1(CO)R2, where R1 and R2 are the same or different hydrocarbon radicals; can be formed during petroleum product oxidation arid can contribute to deposit formation.

K Factor Analysis - method developed by SKF Industries, Inc., a bearing manufacturer, to deter mine the proper lubricant viscosity for specific rolling contact bearing applications in paper machines. It is an import ant means of ensuring maximum bearing life. The K factor is the ratio of the actual lubrication viscosity at operating temperatures to the minimum required lubricant viscosity as determined from SKF data. The analysis is based on several parameters, including bearing size, rotation speed, and exit oil temperature.

kilocalorie - see calorie.


kilowatt-hour - unit of work or energy, equivalent to the energy expended in one hour at a steady rate of one kilowatt. Total kilowatt­ hours (kwh) consumed by one 100 - watt light bulb burning for 150 hours can be calculated as follows: 100 watts x 150 hours = 15,000 wan-hours = 15 kwh.

kinematic viscosity - absolute viscosity of a fluid divided by its density at the same temperature of measurement. It is the measure of a fluid 's resistance to flow under gravity, as determined by test method ASTM D445. To determine kinematic viscosity, a fixed volume of the test fluid is allowed to flow through a calibrated capillary tube (viscometer) that is held at a closely controlled temperature. The kinematic viscosity, in centistokes (cSt), is the product of the measured flow time in seconds and the calibration constant of the viscometer. See viscosity.


kinetic compressor - see compressor.


kinetic pump - see pump.


knock - in the cylinder of a spark-ignited internal combustion engine, premature explosion of a portion of the air-fuel mixture, in dependent of spark plug ignition, as a result of excessive heat and pressure during compression. The high local pressures resulting from the explosion are the source of the objectionable clatter or ping associated with knock. Knock reduces efficiency and can be destructive to engine parts. Knock tendency increases with high ambient temperature, dry atmosphere, low altitude, high barometric pressure, or high-power demands such as hill climbing and trailer towing. High-octane gasolines resist knocking. Also called detonation. See anti-knock, octane number, pre-ignition.



laminating strength - bonding strength of a petroleum wax used as an adhesive between layers of paper or foil, measured in terms of the specific number of grams of force required to peel the layers apart. It is expressed in grams per inch of width of the layers. Sealing strength, similar in meaning to laminating strength, may also be measured in this manner.

lard oil fatty oil used for compounding. See compounded oil.


latent heat - quantity of heat absorbed or released by a substance undergoing a change of state (e.g., ice changing to liquid water, or water to steam) without change of temperature. At standard atmospheric pres­sure, the latent heat of vaporization of water is 2256 kJ/kg (970 Btu/lbs.); this is the amount of energy required to convert water at 100°C (212°F) to steam at the same temperature. Conversely, when steam condenses at 100°C, the same amount of heat is released.

launching lubricant - lubricant applied to inclined launching guides, or ways, to facilitate launching of a ship. Two separate lubricants are usually used: a firm, abrasion-resistant base coat, plus a softer, low-friction slip coat.

LC5O - lethal concentration, 50% mortality; a measure of inhalation toxicity. It is the concentration in air of a volatile chemical compound at which half the test population of an animal species dies when exposed to the compound. It is expressed as parts per million by volume of the toxicant per million parts of air for a given exposure period. See LD50.


LCN - light crude naphtha. See naphtha.


LD5O - lethal dose, 50% mortality, a general measurement of toxicity. It is the dose of a chemical compound that, when administered to laboratory animals, causes death in one- half the test population. It is expressed in milligrams of toxicant per kilogram of animal weight. The route of administration may be oral, epidermal, or intraperitoneal. See LC50.


lead alkyl - any of several lead compounds used to improve octane number in a gasoline. The best known is tetraethyl lead (TEL), Pb (C2H5)4. Another is tetramethyl lead (TML), Pb (CH3)4. Other com­pounds have varying proportions of methyl radicals (CH3) and ethyl radicals (C2H5). Use of lead compounds in motor gasoline is being phased out for environmental reasons. Beginning with the 1980 model year, all new U.S. and foreign-made cars sold in the U.S. required unleaded gasoline.


lead naphthenate, lead oleate - lead soaps that serve as mild EP additives. These additives are seldom used in modern lubricants because of environmental considerations.

lead scavenger - see scavenger.


leaded gasoline - see lead alkyl.


lean and rich octane number - expression of the antiknock value of an aviation gasoline at lean air- fuel mixtures (relatively low concentration of fuel) and rich air-fuel mixtures, respectively. A grade designation of 80/87 means that at lean mixtures the fuel performs like an 80-octane gasoline and at rich mixtures, like an 87-octane gasoline. See performance number.


letterpress - see printing processes.


light crude naphtha - see naphtha.


light ends - low boiling point hydrocarbons in gasoline having up to five carbon atoms, e.g., butanes, butenes, pentanes, pentenes, etc. Also, any extraneous low boiling fraction in a refinery process stream.


limestone - porous, sedimentary rock composed chiefly of calcium carbonate; sometimes serves as a reservoir rock for petroleum.


line blending - in petroleum product manufacture, the mixing of two or more components during transfer through pipelines to a tank or other container. See batch blending.


linear paraffin - see normal paraffin.

liquefied natural gas - see LNG.

liquefied petroleum gas - see LPG.

liquid chromatography - see chromatography.


liter - metric unit of volume equivalent to 1.056 fluid quarts. See metric system.


lithium soap grease - see grease.


lithography - see printing processes.


LMOA Generation 5 Lubricant - see Generation 5 Lubricant.


LMOA (Locomotive Maintenance Officers Association) - trade asso­ciation that promotes the technical interests of the railroad industry; establishes quality and performance standards for petroleum products used by the industry. See Generation 5 lubricant.


LNG (liquefied natural gas) natural gas that has been liquefied at extremely low temperature. It is stored or transported in insulated tanks capable of sustaining the high pressure developed by the product at normal ambient temperatures.

load wear index (LWI) - measure of the relative ability of a lubricant to prevent wear under applied lo ads; it is calculated from data obtained from the Four Ball EP Method. Formerly called mean Hertz load. See four-ball method.


local effect - toxic effect limited to the area of the body (commonly the skin and eyes) that has come in to contact with a toxicant.

Lovibond tintometer - device for measuring the color of a petroleum product, particularly petrolatums. The melted petrolatum is contained in a cell and the color is compared with a series of yellow and red Lovibond glasses. The length of the cell and the color standards that give the best match are reported. See color scale.


lower flammable limit - the concentration of a flammable vapor mixed with air that will just propagate flame, that is, continue to burn. See explosive limits.


low-temperature corrosion - see cold-end corrosion.


LP gas - see LPG.


LPG (liquefied petroleum gas) propane or (less commonly) butane, obtained by extraction from natural gas or from refinery processes. LPG has a vapor pressure sufficiently low to permit compression and storage in a liquid state at moderate pressures and normal ambient temperatures. Pressurized in metal bottles or tanks, LPG is easily handled and readily lends itself to a variety of applications as a fuel, refrigerant, and propellant in packaged aerosols. LPG is also called LP gas and bottled gas. See mercaptan, natural gas liquids.


lubricant - any usually oily liquid or solid that reduces friction, heat, and wear when applied to the surfaces of moving parts. See aluminum rolling oil, anti-seize compound, automatic transmission fluid, block grease. See chain oil, concrete form coaling, compounded oil, coning oil, cutting fluid, cylinder oil, drawing compound. See engine oil, fire-resistant fluid, fire­ resistant grease, gear oil (automotive), gear oil (industrial). See gear shield, graphite, grease, hydraulic fluid, industrial lubricant, in a release agent, launching lubricant See metalworking lubricant, mineral oil, mineral seal oil, mold lubricant. See molybdenum disulfide, multi-grade oil, multi-purpose grease, paper machine oil, rail-flange grease, refrigeration oil. See ring oil, rock drill lubricant, rolling oil, single-grade oil, soluble oil. See straight mineral oil, synthetic lubricant, synthetic turbo oil, thread compound, torque fluid, turbine oil, way lubricant.


lubrication - control of friction and wear by the introduction of a friction-reducing film between moving surfaces in contact. The lubricant used may be a fluid, solid, or plastic substance. For principles of lubrica­tion, see boundary lubrication, full-fluid-film lubrication, ZNIP curve. Also see lubrication methods.


lubrication methods - centralized lubrica­tion, circulating lubrication system, electrohydrodynamic lubrication, force-feed lubrication, full-fluid-film lubrication, gear box. And grease cup, grease gun, mechanical lubricator, oiler, oil mist lubrication, once­ through lubrication, ring oiler, sight fluid. And splash lubrication, squeeze lubrication., ZN/P curve. see boundary lubrication.


lubricity - ability of an oil or grease to lubricate; also, called film strength. Lubricity can by enhanced by additive treatment. See com­pounded oil.


luminometer number - measure of the flame radiation characteristics of a turbine fuel, as determined by test method ASTM D1740. A sample of fuel is burned in a Luminometer lamp, and the temperature rise, at a specified flame radiation value, is compared with the corresponding temperature rise of reference fuels. The higher the luminometer number, the lower the flame radiation and the better the combustion characteristics.

LWI - see load wear index.





machine oil - see once-through lubrication.

marquenching- see quenching.

martempering - see quenching.

mass percent - see weight percent.


mass spectrometer - apparatus for rapid quantitative and qualitative analysis of hydrocarbon compounds in a petroleum sample. It utilizes the principle of accelerating molecules in a circular path in an electrical field. The compounds are separated by centrifugal force, with the molecules having a greater mass (weight) being thrown to the outer periphery of the path. Quantitative measurements are accompli shed by use of either a photographic plate or electronic determination of the relative proportions of each type of particle of a given mass. See chromatography, clay /silica gel analysis, ferrography, infrared analysis, particle count, spectro­graphic analysis.


mastic - any of various semi-solid substances, usually formulated with rubber, other polymers, or oxidized asphalt; commonly used as a tile adhesive caulking, and a sound reducing treatment on various surfaces.

Material Safety Data Sheet (MSDS) - publication containing health and safety information on a hazardous product (including petroleum). The OSHA Hazard Communication Standard requires that an MSDS be provided by manufacturers to distributors or purchasers prior to or at the time of product shipment. An MSDS must include the chemical and common names of all ingredients that have been determined to be health hazards if they constitute 1% or greater of the product's composition (0.1% for carcinogens). An MSDS also includes precautionary guidelines and emergency procedures.

MC asphalt - see cutback asphalt.


mean Hertz load - see load wear index.


mechanical lubricator - once through lubrication device comprising a battery of individual pumps that continuously meter oil to each of several moving parts. It is typically used in steam engines, gas engines, diesel engines and large compressors. The oil is pumped into a sight-feed bowl containing an inert, dense, transparent fluid (see sight fluid) through which the oil floats upward to the feed line. Mechanical lubrication is like centralized lubrication, the principal distinction being that a centralized system is served by a single pump, or by two or more pumps discharging into a common manifold.

mechanical stability - see structural stability.


melting point of wax - temperature at which a sample of wax either melts or solidifies from the solid or liquid state, respectively, depending on the ASTM test used. Low melting point generally indicates low viscosity, low blocking point, and relative softness.

mercaptan - any of a generic series of malodorous, toxic sulfur com­pounds occurring in crude oil; also known as thiols. Mercaptans are removed from most petroleum products by refining but may be added to natural gas and LPG in very low concentrations to give a distinctive warning odor. See hydrogen sulfide odorant.


merit rating - arbitrary graduated numerical rating commonly used in evaluating engine deposit levels when testing the detergent-dispersant characteristics of an engine oil. On a scale of 10 to zero, the lower the number, the heavier the deposits. A less common method of evaluating engine cleanliness is demerit rating. See engine deposits.


metal wetting - see polar compound.


metalworking lubricant - lubricant, usually petroleum-based, that fa­cilitates the cutting or shaping of metal. Basic types of metalworking lubricants are cutting fluids, drawing compounds, and electrical dis­charge machining fluids.


methane - a light, odorless, flammable gas (CH4); the chief constituent of natural gas.


methanol - the lowest molecular weight alcohol (CH3-OH). Also called methyl alcohol and wood alcohol. One of several oxygenates that may be added to motor gasoline to reduce harmful automobile exhaust emissions.

methyl alcohol - see methanol.


methyl tertiary butyl ether - see MTBE.


metric system - international decimal system of weights and measures based on the meter and kilogram.

micro carbon residue - see carbon residue.


microcrystalline wax, microwax - see wax (petroleum).


microcoulometry - highly sensitive and precise electro-chemical analyti­cal technique that can measure microgram quantities of sulfur and chlorine in a solvent. A minute quantity of solvent is combusted in a quartz pyrolysis tube, and the combustion products - typically carbon dioxide (CO 2), water, sulfur dioxide (S02) , and hydrogen chloride (HCl) - flow to a titration cell. In the test for sulfur, the SO2 reacts with iodine in the cell, creating an electrical imbalance that is detected by sensor electrodes. The iodine is then restored to its original concentration by means of a current produced at generator electrodes by a microcoulometer. The amount of current and time required to restore the system to equilibrium is directly proportional to the amount of sulfur present in the solvent sample. In the test for chlorine, the HCl reacts in the titration cell with silver ions.

microemulsion - translucent oil-in-water emulsion made up of very fine droplets; compared with conventional emulsions, a micro-emulsion is more stable, particularly in hard water, and more resistant to bacterial attack.

micron - unit of length equal to one- millionth of a meter. See metric system.


mid-boiling point - see distillation test.


middle distillate - see distillate.


military specifications for engine oils - There are military specifications for engine oils. Although many are obsolete, they are still commonly used to designate required engine oil performance levels. To qualify under a military specification, an oil must meet minimum require­ments in laboratory engine tests. In most cases these are the same ASTM tests used to define API Engine Service Categories.


mineral oil - any petroleum oil, as contrasted to animal or vegetable oils. Also, a highly refined petroleum distillate, or white oil, used medicinally as a laxative.

mineral seal oil distillation fraction between kerosene and gas oil, widely used as a solvent oil in gas absorption processes (see absorber oil), as a lubricant for the rolling of metal foil, and as a base oil in many specialty formulations. Mineral seal oil takes its name - not from any sealing function - but from the fact that it originally replaced oil derived from seal blubber for use as an illuminant for signal lamps and lighthouses.

mineral spirits - naphthas with mixed hydrocarbon composition and intermediate volatility. They boil within the range of 149°C (300°F) to 204°C (400°F) and possess a flash point over 38°C (100°F). They are broadly used as solvents or thinners in making cleaning products, paints, lacquers, inks, and rubber. Also used uncompounded for cleaning metal and fabrics.

miscible - capable of being mixed in any concentration without separa­tion of phases. E.g., water and ethyl alcohol are miscible. See immiscible.


mist lubrication - see oil mist lubrication.


mobilometer - device for measuring the relative consistency or resistance to flow of fluid grades of grease too soft to be tested in the penetrometer. See consistency (grease).


mold lubricant - a compound, often of petroleum origin, for coating the interiors of molds for glass and ceramic products. The mold lubricant facilitates removal of the molded object from the mold, protects the surface of the mold, and reduces or eliminates the need for cleaning it. Also called release agent.


molecular weight - The sum of the atomic weights of a molecule's constituent atoms. The molecular weight of a chemical compound is often expressed in terms of "average molecular weight," i.e., the average weight of all the molecules in the compound. In describing a hydrocarbon, average molecular weight is commonly defined in terms of the compound's boiling point or distillation range, since these characteristics normally reflect the size, or heaviness, of the average molecule. See distillation test.


molybdenum disulfide - a black, lustrous powder (MoS2) that serves as a dry-film lubricant in certain high-temperature and high-vacuum appli­cations. It is also used in the form of pastes to prevent scoring when assembling press-fit parts, and as an additive to impart residual lubrication properties to oils and greases. Molybdenum disulfide is often called moly.


monomer - see polymer.


Motor Octane Number - see octane number.


motor oil - see engine oil.


MS asphalt - see emulsified anionic asphalt.


MSDS - see Material Safety Data Sheet.


MTBE (methyl tertiary butyl ether) - one of several oxygenates that are useful in reducing harmful automobile exhaust emissions. See antiknock compounds.


mud-liquid circulated through the borehole during rotary drilling; it is used to bring cuttings to the surface, cool and lubricate the drill stem, protect against blowouts by holding back subsurface pressures, and prevent fluid loss by plastering the borehole wall. Mud formulations originally were suspensions of clay or other earth solid in water, but today are more complex mixtures of liquids (not necessarily water), reactive solids, and inert solids. See drilling oil.


multi-grade oil - engine oil that meets the requirements of more than one SAE viscosity grade classification and may therefore be suit able for use over a wider temperature range than a single-grade oil. Multi-grade oils have two viscosity grade numbers indicating their lowest and highest classification, e.g., SAE lOW-40. The lower grade number indicates the relative fluidity of the oil in cold weather for easy starting and immediate oil flow. The higher-grade number indicates the relative viscosity of the oil at high operating temperatures for adequate wear protection. The " W" means " winter" grade. Multi -grade oils generally contain viscosity index (V.I.) improvers that reduce the tendency of an oil to lose viscosity, or thin out, at high temperatures. See SAE engine oil viscosity classification.


multi-purpose grease - high-quality grease that can be used in a variety of applications.

multi-stage compressor - see compressor.




naphtha - generic, loosely defined term covering a range of light petroleum distillates (see distillation). Included in the naphtha classifica­tion are gasoline blending stocks, mineral spirits, and a broad selection of petroleum solvents. In refining, the term light crude naphtha (LCN) usually refers to the first liquid distillation fraction, boiling range 32°F to 100°C (90°F to 175°F), while heavy crude naphtha is usually the second distillation fraction, boiling range 163°C to 218°C (325°F to 425°F).

naphthene hydrocarbon characterized by saturated carbon atoms in a ring structure and having the general formula CnH2n; also called cyclo­paraffin or cycloalkane. Naphthenic lubricating oils have low pour points, owing to their very low wax content, and good solvency properties. See saturated hydrocarbon.


naphthenic - see naphthene.

narrow cut - see distillation test.

National Formulary - see NF.

National Marine Manufacturers Association (NMMA) - formerly called Boating Industry of America) technical society of builders and suppliers of two-stroke-cycle engines; develops and licenses quality standards for water-coo led two-stroke-cycle engine lubricants.

natural gas - naturally occurring mixture of gaseous saturated hydro­ carbons, consisting of 80-95% methane (CH4), lesser amounts of pro­pane, ethane and butane, and small quantities of non-hydrocarbon gases (e.g., nitrogen, helium). Natural gas is found in sandstone, limestone, and other porous rocks beneath the earth's surface, often in association with crude oil. Because of its high heating value and clean-burning characteristics, natural gas is widely used as a fuel. The heavier hydrocarbons in natural gas can be extracted, through compression or absorption processes, to yield LPG (propane or butane), natural gasoline, and raw materials for petrochemical manufacture. See gas engine, natural gas liquids.


natural gas liquids hydrocarbons extracted from natural gas: prima­rily LPG (propane or butane) and natural gasoline, the latter being commonly blended with crude-derived gasoline to improve volatility. Natural gas liquids can be separated from lighter natural gas hydrocarbons. This separation can happen through compression or absorption. In compression, the gas is compressed and cooled. This causes heavier hydrocarbons to liquefy. Absorption works differently. The gas mixes with a petroleum distillate, like kerosene. This distillate absorbs or dissolves the heavier hydrocarbons.

natural gasoline - liquid hydrocarbons recovered from wet natural gas; also called casing head gasoline. See natural gas liquids.

natural rubber - resilient elastomer generally prepared from the milky sap, or latex, of the rubber tree (hevea brasilensis). Natural rubber possesses a degree of tack (adhesive properties) not inherent in most synthetic rubbers. It may be used unblended in large tires for construction and agricultural equipment and airplanes, where low rolling resistance and low heat buildup are of greater importance than wear resistance. In the manufacture of tires for highway vehicles, natural rubber may be added to synthetic rubber to provide the necessary tack.

naturally aspirated engine - engine in which the intake air entering the system is at atmospheric pressure.

NBR - see nitrile rubber.


neoprene rubber (CR) - synthetic rubber, a chloroprene polymer, with excellent resistance to weather, oil, chemicals, and flame. Widely used for electrical cable insulation, industrial hose, adhesives, shoe soles, and paints.

neutralization number - also called “neut” number. An indication of the acidity or alkalinity of an oil. The number is the weight in milligrams of the amount of acid (hydrochloric acid) or base (potassium hydroxide). These are required to neutralize one gram of the oil. This in accordance with test method ASTM D664 (potentiometric method) or ASTM D974 (colori­metric method). Strong acid number is the weight in milligrams of base required to titrate a one-gram sample up to a pH of 4; total acid number is the weight in milligrams of base required to neutralize all acidic constituents. Strong base number is the quantity of acid, expressed in terms of the equivalent number of milligrams of KOH, required to titrate a one-gram sample to specific pH; total base number is the milligrams of acid, expressed in equivalent milligrams of KOH, to neutralize all basic constituents. If the neutralization number indicates increased acidity (i.e., high acid number) of a used oil, this may indicate that oil oxidation, additive depletion, or a change in the oil's operating environment has occurred.

newton - in the Systeme International, the unit of force required to accelerate a mass of one kilogram one meter per second.

Newtonian fluid - fluid, such as a straight mineral oil, whose viscosity does not change with rate of flow. See shear stress.


NF (National Formulary) - listing of drugs, drug formulas, quality standards, and tests published by the United States Phaimacopeial Convention, Inc., which also publishes the USP (United States Pharmacopeia). The purpose of the NF is to ensure the uniformity of drug products and to maintain and upgrade standards of drug quality, packaging, labeling, and storage. In 1980, all NF responsibility for white oil classification was transferred to the USP.

Niemann four-square gear oil test - see FZG four-square gear oil test.


nitration - in internal combustion engines, the formation of nitrogen oxides (NOx) during fuel combustion. NOx reacts with water in the crankcase to form nitrous acid (HN02), which can degrade the oil and increase oil viscosity, Nitration is a particular problem in gas engines due to relatively high combustion chamber temperatures.

nitration grade - term for toluene, xylene, or benzene refined und er close controls for very narrow boiling range and high purity. Nitration­ grade specifications for the three solvents are given in test methods ASTM D841, D843, and D835, respectively.

nitrile rubber (NBR) - synthetic rubber made by the copolymerization of butadiene and acrylonitrile. It resists heat, oil, and fuels; hence, is used in gasoline and oil hose, and in tank linings. Originally called Buna-N.

nitrogen blanket - see gas blanket.


nitrogen oxides (NOx) - nitric oxide (NO), with minor amounts of nitrogen dioxide (NO2). NOx is formed whenever fuel is burned at high temperatures in air, from nitrogen in the air as well as in the fuel. Motor vehicles and stationary combustion sources (furnaces and boilers) are the primary man-made source s, although automotive emission controls are reducing the automobile's contribution. Natural emissions of NOx arise from bacterial action in the soil. NOx can react with hydrocarbons to produce smog. See catalytic converter, emissions (automotive), emissions (stationary source), pollutants, hydrocarbon emissions, nitration, volatile organic compound.


NLGI Automotive Grease Classifications - automotive lubricating grease quality levels established jointly by SAE, ASTM, and NLGI. There are two categories: Chassis Lubricants and Wheel Bearing Lubricants. Quality or performance levels within each category are defined by ASTM tests.

NLGI (National Lubricating Grease Institute) - trade association whose main interest is grease and grease technology. NLGI is best known for its system of rating greases by penetration. See NLGI consistency grades, penetration (grease).


NLGI consistency grades - simplified rating system for grease. This system was established by the National Lubricating Grease Institute (NLGI). The rating ranges from 000 - representing semi-fluid - to 6, which signifies block grease. See penetration (grease).

NMMA - see National Marine Manufacturers Association.


non-Newtonian fluid - fluid, such as a grease or a polymer containing oil (e.g., multi-grade oil), in which shear stress is not proportional to shear rate. See Brookfield viscosity.


non-soap thickener - see grease.


non-volatiles - see solids content.


normal paraffin - hydrocarbon consisting of unbranched molecules in which any carbon atom is attached to no more than two other carbon atoms; also called straight chain paraffin and linear paraffin. See iso-paraffin, paraffin.



occupational exposure limit (OEL) - the time-weighted average con­centration of a material in air for an eight-hour workday, 40-hour work­ week to which nearly all workers may be exposed repeatedly without adverse effect. Also called threshold limit value (TLV).


Occupational Safety and Health Act of 1970 - the main legislation affecting health and safety in the workplace. It created the Occupational Safety and Health Administration (OSHA) in the Department of Labor, and the National Institute for Occupational Safety and Health in the Department of Health and Human Services (formerly the Department of Health, Education, and Welfare).

OCS - see outer continental shelf.


octane number - expression of the antiknock properties of a gasoline, relative to that of a standard reference fuel. There are two distinct types of octane number measured in the laboratory: Research Octane Number (RON) and Motor Octane Number (MON), determined in accordance with ASTM D2699 and D2700, respectively. Both the RON and MON tests are conducted in the same laboratory engine, but RON is determined under less severe conditions, and is therefore numerically greater than MON for the same fuel. The average of the two numbers - (RON + MON)/2 - is commonly used as the indicator of a gasoline’s road antiknock performance. The gasoline being tested is run in a special single-cylinder engine, whose compression ratio can be varied (the higher the compression ratio, the higher the octane requirement). The knock intensity of the test fuel, as measured by a knock-meter, is compared with the knock intensities of blends of isooctane (assigned a knock rating of 100) and heptane (with a knock rating of zero), measured under the same conditions as the test fuel. The percentage, by volume, of the isooctane in the blend that matches the characteristics of the test fuel is designated as the octane number of the fuel. For example, if the matching blend contained 90% isooctane, the octane number of the test fuel would be 90. In addition to the laboratory tests for RON and MON, there is a third method, Road Octane Number, which is conducted in a specially equipped test car by individuals trained to hear trace levels of engine knock. See antiknock compounds, knock.


odorant - a chemical, usually a mercaptan, that is added to natural gas and LPG so that the presence of the gas can be detected by smell.

odorless solvents solvents, generally mineral spirits, that are synthe­sized by alkylation and refined to remove odorous aromatics and sulfur compounds; there remains, however, a relatively low level of odor inherent in the hydrocarbons. Odorless solvent applications include dry cleaning and odorless paint manufacture.

odor panel- a group of individuals trained to identify and rate odors to check the odor quality of solvents, waxes, etc.

OEL - see occupational exposure limit.


OEM - original equipment manufacturer; maker of any engine, machine, or other device, or any component of such equipment. OEMs commonly specify the type and quality of petroleum product to be used with their equipment.

offset printing - see printing processes.


oil content of petroleum wax - a measure of wax refinement, under conditions prescribed by test method ASTM D721. The sample is dissolved in methyl ethyl ketone and cooled to -32°C (-26°F) to precipitate the wax, which is then filtered out. The oil content of the remaining filtrate is determined by evaporating the solvent and weighing the residue. Generally, waxes with an oil content of 1.0 mass percent or less are known as refined waxes. Refined waxes are harder and have greater resistance to blocking (see blocking point) and staining than waxes with higher oil content. Waxes with an oil content up to 3.0 mass percent are generally referred to as scale waxes, and are used in applications where the slight color, odor, and taste imparted by the higher oil content can be tolerated. Semi-refined slack waxes may have oil contents up to 30 mass percent and are used in non-critical applications. The distinction between scale and slack waxes at intermediate oil content levels (2-4 mass percent) is not clearly defined, and their suitability for applications depends upon properties other than oil content alone.

oil dilution - the dilution of the lubricating oil by fuel or partially combusted fuel, which can find its way past the piston rings into the crankcase, particularly during cold starting. The lighter portions of the fuel are evaporated off as the oil heats up, but the remaining material can reduce lubricating performance and, hence, increase wear.

oil drain interval - time between oil drains from a sump or crankcase. Oil drain intervals may vary widely depending on the type of oil and the application. Some premium quality turbine oils can remain in service for decades without an oil change, whereas an automotive engine oil may require changing after several months of engine operation. Following recommended oil drain intervals is essential to maintaining an oil's ability to lubricate and prevent deposit buildup on critical parts. See engine deposits.


oiler - device for once-through lubrication. Three common types of oilers are: drop-feed, wick-feed, and bottle-feed; all depend on gravity to induce a metered flow of oil to the bearing. The drop-feed oiler delivers oil from the bottom of a reservoir to a bearing one drop at a time; flow rate is controlled by a needle valve at the top of the reservoir. In a wick-feed oiler, the oil flows up a wick and drips from the end of the wick into the bearing; feed is regulated by changing the number of strands, by raising or lowering the oil level, or by applying pressure to the wick. In a bottle-feed oiler, a vacuum at the top of the jar keeps the fluid from running out; as tiny bubbles of air enter, the vacuum is reduced, and a small amount of oil enters the bearing or is added to a reservoir from which the bearing is lubricated. See centralized lubrication, mechanical lubricator, ring oiler.


oiliness agent polar compound used to increase the lubricity of a lubricating oil and aid in preventing wear and scoring under conditions of boundary lubrication.


oil mist lubrication - type of centralized lubrication that employs compressed air to transform liquid oil into a mist that is then distributed at low pressure to multiple points of application. The oil mist is formed in a "generator," where compressed air is passed across an orifice, creating a pressure reduction that causes oil to be drawn from a reservoir into the airstream. The resulting mist (composed of fine droplets on the average of 1.5 microns) is distributed through feed lines to various application points. Here, it is reclassified, or condensed, to a liquid, spray, or coarser mist by specialized fittings, depending on the lubrication requirements. Oils for use in a mist lubrication system are formulated with carefully selected base stocks and additives for maximum delivery of oil to the lubrication points and minimal coalescence of oil in the feed lines.

oil shale - shale containing a rubbery hydrocarbon known as kerogen. When shale is heated, the kerogen vaporizes and condenses as tar-like oil called shale oil, which can be upgraded and refined into products in much the same way as liquid petroleum.

olefin - any of a series of unsaturated, relatively unstable hydrocarbons characterized by the presence of a double bond between two carbon atoms in its structure, which is commonly straight-chain or branched. The double bond is chemically active and provides a focal point for the addition of other reactive elements, such as oxygen. Due to their ease of oxidation, olefins are undesirable in petroleum solvents and lube oils. Examples of olefins are ethylene and propylene. See unsaturated hydrocarbon.


olefin oligomer - synthetic lubricant base, formed by the polymerization of olefin monomers (see polymer); properties include good oxidation stability at high temperatures, good hydrolytic stability, good compatibility with mineral oils, and low volatility. Used in turbines, compressors, gears, automotive engines, and electrical applications.

once-through lubrication - system of lubrication in which the lubricant is supplied to the lubricated part at a minimal rate and is not returned or recirculated. Lubrication by oil can, mechanical lubricator, centralized grease system, lubricating device, oil mist, etc., is done on a once-through basis. Since the lubricant is not recovered, high oxidation stability and long service life are usually not necessary, but viscosity and other proper­ties may be very important. Oils that meet the moderate requirements of once-through lubrication are known variously as machine oils and gen­eral purpose oils. See centralized lubrication, chain oil, cylinder oil, oiler, oil mist lubrication.


OPEC (Organization of Petroleum Exporting Countries) - group of oil-producing nations. Founded in 1960, its goal is to advance member interests when interacting with industrialized oil-consuming nations. The OPEC mem­bers are Algeria, Gabon, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, United Arab Emirates, and Venezuela. Rising world oil demand, tight world oil supplies, and declining U.S. oil and gas production have enabled OPEC to dramatically increase the price of its oil exports since 1973.

open cup - see Cleveland open cup, Tag open cup.


open gear- gear that is exposed to the environment, rather than being housed in a protective gear box. Open gears are generally large, heavily loaded, and slow moving. They are found in such applications as mining and construction machinery, punch presses, plastic and rubber mills, tube mills, and rotary kilns. Open gears require viscous, adhesive lubricants that bond to the metal surfaces and resist run-off. Such lubricants are often called gear shields. Top-quality lubricants for such applications are specially formulated to protect the gears against the effects of water and other contaminants.

orchard spray oil - petroleum oil suitable for emulsifying with water to form an insecticide spray that kills orchard pests by suffocation. When applied to fruit trees as directed, it has proved highly effective in the control of certain insects that attack citrus, apples, pears, peaches, nuts, and other orchard crops. The phytotoxicity (harmfulness to plants) of the oil depends on the oil's boiling range and purity. Purity is broadly defined by the unsulfonated residue of the oil. Oils with an unsulfonated residue of 92% or higher can be used in sensitive applications, such as verdant, or summer sprays when trees are in leaf. These are known as "superior" spray oils. Oils with lower unsulfonated residues - at least 80% - are called "regular" spray oils and are limited to application only in the dormant phase of plant growth. See agricultural oil.


organic compound - chemical substance containing carbon and hydro­gen; other elements, such as nitrogen or oxygen, may also be present. See hydrocarbon, inorganic compound.


Organization of Petroleum Exporting Countries - see OPEC.


OSHA Hazard Communication Standard - See Hazard Communica­tion Standard.


OSHA (Occupational Safety and Health Administration) - See Occupational Safety and Health Act of 1970.


Otto cycle - four-stroke engine cycle. See internal combustion engine.


outer continental shelf - the part of the continental margin that slopes gradually away from the shore to a point where a much steeper drop begins. The outer continental shelf may extend from a few miles to several hundred miles from the shore. It is much wider off the U.S. East and Gulf coasts, for example, than off the West Coast. Much of the remaining U.S. oil and gas resources are believed to lie beneath the outer continental shelf.

overhead - the distillation fraction removed as vapor or liquid from the top of a distillation column or pipe still.

oxidation - the chemical combination of a substance with oxygen. All petroleum products are subject to oxidation, with resultant degradation of their composition and performance. The process is accelerated by heat, light, metal catalysts (e.g., copper), and the presence of water, acids, or solid contaminants. The first reaction products of oxidation are organic peroxides. Further oxidation can be catalyzed by peroxides. This forms alcohols, aldehydes, ketones, and organic acids. These substances can be oxidized further, leading to high-molecular-weight, oil-insoluble polymers. These settle out as sludges, varnishes, and gums that can impair equipment operation. The organic acids formed from oxidation are corrosive to metals. Oxidation resistance of a product can be improved by careful selection of base stocks (paraffins have greater oxidation resistance than naphthenes), special refining methods, and addition of oxidation inhibitors. Also, oxidation can be minimized by good maintenance of oil and equipment to prevent contamination and excessive heat. See engine deposits, gum in gasoline, oxidation stability.


oxidation inhibitor - substance added in small quantities to a petroleum product to increase its oxidation resistance, thereby lengthening its service or storage life; also called antioxidant. An oxidation inhibitor may work in one of three ways: (1) by combining with and modifying peroxides (initial oxidation products) to render them harmless, (2) by decomposing the peroxides, or (3) by rendering an oxidation catalyst (metal or metal ions) inert.

oxidation stability - resistance of a petroleum product to oxidation; hence, a measure of its potential service or storage life. There are several ASTM tests to determine the oxidation stability of a lubricant or fuel, all of which are intended to simulate service conditions on an accelerated basis. In general, the test sample is exposed to oxygen or air at an elevated temperature, and sometimes to water or catalysts (usually iron or copper). Depending on the test, results are expressed in terms of the time required to produce a specified effect (such as a pressure drop), the amount of sludge or gum produced, or the amount of oxygen consumed during a specified period. See gum in gasoline.


oxidized asphalt - also called blown asphalt. See asphalt.


oxygenate - an organic chemical compound whose molecular structure contains oxygen in addition to carbon and hydrogen. Certain oxygenates, such as MTBE, ethanol, and methanol, may be added to motor gasoline to reduce carbon monoxide (CO) emissions in automobile exhaust. Oxygen­ates reduce harmful emissions by providing excess oxygen to promote more complete combustion of the fuel. See emissions (automotive).


ozone - triatomic (O3allotrope of oxygen (O2); unstable blue gas with a pungent, irritating odor. Ozone is formed from oxygen by electric discharge (e.g., lightning) or by ultraviolet radiation (part of the solar spectrum). A layer of ozone in the upper atmosphere protects the earth from excessive exposure to ultraviolet radiation. Ground-level ozone, formed when volatile organic compounds react with nitrogen oxides in the presence of sunlight, is a major component of photochemical smog.


pale oil - straight naphthenic mineral oil, straw, or pale yellow in color, used as a once-through lubricant and in the formulation of process oils. See naphthene, straight mineral oil, once-through lubrication.


paper machine oil - premium lubricant formulated to perform depend­ably under the hot, wet conditions of paper machine operation. The oil must have outstanding resistance to oxidation and thermal decomposition, potent detergency to prevent deposit build upon hot surfaces, and excellent demulsibilitv and rust protection. It also must be readily filterable through filters with porosity as fine as six microns. These features, derived from a careful blending of additives and high-quality base stock, are essential to extending equipment life and reducing costly unscheduled downtime. See detergent, rust inhibitor, thermal stability.


paraffin - hydrocarbon identified by saturated straight (normal) or branched (iso) carbon chains; also called an alkane. The generalized paraffinic molecule can by symbolized by the formula CnH2n+2. Paraffins are relatively non-reactive and have excellent oxidation stability. In contrast to naphthenic (see naphthene) oils, paraffinic lube oils have relatively high wax content and pour point, and generally have a high viscosity index (V. I.). Paraffinic solvents are generally lower in solvency than naphthenic or aromatic solvents. See hydrocarbon, normal paraffin, isoparaffin, saturated hydrocarbon.


paraffinic - see paraffin.


paraffin wax - petroleum-derived wax usually consisting of high­ molecular-weight normal paraffins. Distinct from other natural waxes, such as beeswax and carnauba wax (palm tree), which are composed of high-molecular -weight esters. This in combination with high-molecular-weight acids, alcohols, and hydrocarbons.

partial pressure - pressure exerted by a single component of a gaseous mixture. The sum of the partial pressures in a gaseous mixture equals the total pressure. The partial pressure of a substance is a function both of its volatility, or vapor pressure, and its concentration.

particle count- technique for detecting and categorizing particles in a used lube oil resulting from wear or contamination. In the test, an oil sample flows through a small orifice with a light source on one side and an optical sensor on the other. The pulse gene rated by interruption of the light source is proportional to the size of each particle. Large particles, greater than 10-15 microns, portend fatigue-related catastrophic equipment failure. See chromatography, ferrography, infrared analysis, spectrographic analysis.


particulates - atmospheric particles made up of a wide range of natural materials (e.g., pollen, dust, resins), combined with man-made pollutants (e.g., smoke particles, metallic ash); in sufficient concentrations, particu­late scan be a respiratory irritant. Primary sources of man-ma de particulate emissions are industrial process losses (e.g., from cement plants) and stationary combustion sources. Motor vehicles contribute a relatively minor number of particulates. See emissions (stationary source), pollut­ants.


pascal (Pa) - in the Systeme International, a unit of pressure equivalent to a force of one newton (n) applied to an area of one square meter.

paving asphalt - see asphalt cement.


PCB - refers to polychlorinated biphenyl, which is a category of synthetic chemicals. This group includes a series of compounds, ranging from monochlorobiphenyl to decachlorobiphenyl. PCBs do not occur naturally in petroleum but have been found as contaminants in used oil. PCBs have been legally designated as a health hazard, and any oil so contaminated must be handled in strict accordance with state and federal regulations.

PCV - see positive crankcase ventilation.


PE - see polyethylene.


penetration (asphalt) - method for gauging the consistency of semi-solid bituminous materials. See penetration grading (asphalt), viscosity (asphalt).

penetration (grease) - measure of the consistency of a grease, utilizing a penetrometer. Penetration is reported as the tenths of a millimeter (penetration number) that a standard cone, acting under the influence of gravity, will penetrate the grease sample under test conditions prescribed by test method ASTM D217. Standard test temperature is 25°C (77°F). The higher the penetration number, the softer the grease. Undisturbed penetration is the penetration of a grease sample as originally received in its container. Unworked penetration is the penetration of a grease sample that has received only minimal handling in transfer from its original container to the test apparatus. Worked penetration is the penetration of a sample immediately after it has been subjected to 60 double strokes in a standard grease worker; other penetration measurements may utilize more than 60 strokes. Block penetration is the penetration of block grease (grease sufficiently hard to hold its shape without a container).

penetration (wax) - measure of the hardness of a petroleum wax, utilizing a penetrometer. Penetration is reported as the depth, in tenths of millimeter, to which a standard needle penetrates the wax under conditions described in test method ASTM D1321. Prior to penetration, the wax sample is heated to 17°C above its congealing point, air cooled, then conditioned at test temperature in a water bath, where the sample remains during the penetration test. The test temperature may range from 25° to 75°C.

penetration grading (asphalt) - classification system for asphalt ce­ment, defined in AASHTO (American Association of State Highway Transportation Officials) Specification M20, and based on tests for penetration (asphalt), flash point, ductility, purity, etc., as specified in test method ASTM D946. There are five standard grades, ranging from hard to soft: 40-50, 60-70, 85-100, 120-150, and 200-300. Asphalt cement is also classified by viscosity grading.


penetrometer - apparatus for mea­suring the consistency of lubricating grease or asphalt. A standard cone (for grease) or needle (for wax or asphalt) is lowered on to a test sample, under prescribed conditions, and the depth of penetration is measured. See penetration (asphalt), penetration (grease), penetration (wax).


Pensky-Martens closed tester - apparatus used in determining the flash point of fuel oils and cutback asphalt under conditions prescribed by test method ASTM D93. The test sample is slowly heated in a closed cup, at a specified constant rate, with continual stirring. A small flame is introduced into the cup at specified intervals through shuttered openings. The lowest temperature at which the vapors above the sample briefly ignite is the flash point. See Tag closed tester.


pentane - saturated paraffinic hydrocarbon (C5H12); it is a colorless, volatile liquid, normally blended into gasoline. See paraffin, saturated hydrocarbon. 

performance number - expression of the antiknock properties of an aviation gasoline with a Motor Octane Number higher than 100. The lab procedure to determine performance number follows the Motor Octane Number method. But performance number relies on milliliters of tetraethyl lead in the reference isooctane blend. This blend matches the antiknock characteristics of the test fuel. A 100/130 grade aviation gasoline has an octane number of 100 at lean fuel mix and a performance number of 130 at rich mix. See lean and rich octane numbers.


peroxide - any compound containing two linked oxygen atoms (e.g., Na202) that yields hydrogen peroxide (H202) when reacted with acid. Relatively unstable, peroxides are strong oxidizing agents and, when present in lubricating oils, can accelerate oil oxidation and promote bearing corrosion. See corrosion.


pesticide - any chemical substance intended to kill or control pests. Common pesticides are insecticides, rodenticides, herbicides, fungicides, and bactericides. Petroleum products and their petrochemical derivatives are important in the formulation of many types of pesticides. Specialized petroleum oils are used to kill insects by suffocation (see orchard spray oil); other petroleum products serve as solvents or diluents for the active component. See agricultural oil.


petrochemical - any chemical derived from crude oil, crude products, or natural gas. A petrochemical is basically a compound of carbon and hydrogen but may incorporate many other elements. Petrochemicals are used in the manufacture of numerous products such as synthetic rubber, synthetic fibers (such as nylon and polyester), plastics, fertilizers, paints, detergents, and pesticides.


petrolatum - semi-solid, waxy hydrocarbon, pale to yellow in color, composed primarily of high-molecular-weight waxes; used in lubricants and rust preventives. Derived from dewaxing of high-viscosity base oils, such as bright stock. See wax (petroleum).


petroleum - term applied to crude oil and its products.


pH - measure of the acidity or alkalinity of an aqueous solution. The pH scale ranges from 0 (very acidic) to 14 (very alkaline), with a pH of 7 indicating a neutral solution equivalent to the pH of distilled water. See neutralization number.


phenol - white crystalline compound (C6H5OH) derived from benzene, used in the manufacture of phenolic resins, weed killers, plastics, disinfec­tants; also used in solvent extraction, petroleum refining process. Phenol is a toxic material; skin contact must be avoided.

phosphate ester - any of a group of synthetic lubricants having superior fire resistance. A phosphate ester generally has poor hydrolytic stability, poor compatibility with mineral oil, and a relatively low viscosity index (V.l.). It is used as a fire-resistant hydraulic fluid in high-temperature applications.

phytotoxicity - injuriousness to plants. Phytotoxic effects can include leaf injury, leaf drop, retarded growth, and reduced amount or quality of fruit. See agricultural oil.


pig - solid plug inserted into pipelines and pushed through by fluid pressure. It may be used for separating two fluids being pumped through the line, or for cleaning foreign materials from a line.

pinion - see gear.


pipe still - see distillation.


piston sweep - see sweep (of a piston).


plain bearing - see bearing.


planography - see printing processes.


plasticity - the property of an apparently solid material that enables it to be permanently deformed under the application of force, without rupture. (Plastic flow differs from fluid flow in that the shear stress must exceed a yield point before any flow occurs.)

plasticizer - any organic compound used in modifying plastics, syn­thetic rubber, and similar materials to incorporate flexibility and tough­ness.

plastisols and organosols - coating materials composed of resins suspended in a hydrocarbon liquid. An organosol is a plastisol with an added solvent, which swells the resin particles, thereby increasing viscos­ity. Applications include spray coating, dipping, and coatings for alumi­num, fabrics, and paper.

Platinum-Cobalt system - see color scale.


PNA (polynuclear aromatic) - any of numerous complex hydrocarbon compounds consisting of three or more benzene rings in a compact molecular arrangement. Some types of PNA's are known to be carcino­genic (cancer causing). PNA's are formed in fossil fuel combustion and other heat processes, such as catalytic cracking. They can also form when foods or other organic substances are charred. PNA's occur naturally in many foods, including leafy vegetables, grain cereals, fruits, and meats.

pneumatic - tool-machine powered by an air motor driven by compressed air. Pneumatic power is used to drive a wide range of tools, both those requiring rotary motion, such as drills, and those requiring reciprocating motion, e.g., hammers and chisels. Pneumatic tool lubricants are generally the same types as those for compressors; however, the percussion forces in some pneumatic tools may demand special lubricants with EP proper­ ties. See EP additive, rock drill lubricant.


poise - see viscosity.


polar compound - a chemical compound whose molecules exhibit electrically positive characteristics at one extremity and negative charac­teristics at the other. Polar compounds are used as additives in many petroleum products. Polarity gives certain molecules a strong affinity for solid surfaces; as lubricant additives (oiliness agents), such molecules plate out to form a tenacious, friction-reducing film. Some polar molecules are oil-soluble at one end and water-soluble at the other end; in lubricants, they act as emulsifiers, helping to form stable oil-water emulsions. Such lubricants are said to have good metal-wetting properties. Polar com­pounds with a strong attraction for solid contaminants act as detergents in engine oils by keeping contaminants finely dispersed.

pollutants (atmospheric) - any substances released to the environment that threaten health or damage vegetation if present in sufficient concen­tration. The major pollutants emitted as a result of man's industrial activity (largely through the combustion of fossil fuels) are sulfur oxides - predominantly sulfur dioxide (SO2) - nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and particulates. Such pollutants have a relatively short residence in the atmosphere before being removed by natural scavenging processes. SO2, for example, has an atmospheric residence time of about four days. There has thus been no evidence of a global buildup of these pollutants. In a given locality, however, pollutants can reach high concentrations in the atmosphere, causing respiratory ailments, as well as inhibiting growth of vegetation, turning soil acid, eroding masonry in buildings, and corroding metals. See emissions (automotive), emissions (stationary source).


polyalphaolefin - see synthetic lubricant.


polybutadiene rubber (BR) - one of the stereo rubbers, a term desig­nating high uniformity of composition. High in abrasion resistance, BR is blended with styrene-butadiene rubber (SBR) for tire tread manufacture. See synthetic rubber.


polyester - any of several synthetic resins usually produced by the polymerization of dibasic acid with a dihydric alcohol (see polymer). Polyester resins have high sealing strength and are weather resistant. They are used in the manufacture of boat hulls, waterproof fibers, and adhesives.

polyethylene (PE) - polymerized ethylene (see polymer), ranging from a colorless liquid to a white solid; used in the manufacture of plastic films and sheets, and a wide variety of containers, kitchenware, tubing, etc.

polyglycols polymers of ethylene or propylene oxides used as a synthetic lubricant base. Properties include very good hydrolytic stability, high viscosity index (V.l.), and low volatility. Used particularly in water emulsion fluids.

polyisoprene rubber (IR) - one of the stereo rubbers, a term designat­ing a high uniformity of composition. Sometimes called "synthetic natural rubber" because of its similar chemical composition, high tack, resiliency, and heat resistance. It can replace natural rubber in many applications. See polyolefin, rubber, synthetic rubber.


polymer - substance formed through polymerization. This links two or more simple, unsaturated monomer molecules. The resulting heavier molecule retains the same elements in the same proportions as the original monomers. This means each monomer preserves its structural identity. A polymer may be liquid or solid; solid polymers may consist of millions of repeated linked units. A polymer made from two or more dissimilar monomers is called a copolymer; a copolymer composed of three different types of monomers is a terpoly­mer. Natural rubber and synthetic rubbers are examples of polymers. Polymers are commonly used as viscosity index improvers in multi-grade oils.


polymerization - in petroleum refining, polymerization refers to the combination of light, gaseous hydrocarbons, usually olefins, into high­ molecular-weight hydrocarbons that are used in manufacturing motor gasoline and aviation fuel. The product formed by combining two identi­cal olefin molecules is called a dimer, and by three such molecules, a trimer. See polymer.


polymer-modified asphalt (PMA) asphalt binders (or cements) for paving, roofing, or industrial use, blended with a polymer to impart premium performance. For example, a PMA may provide increased stiffness to reduce asphalt pavement rutting at high temperatures.


polyolefin polymer derived by polymerization of relatively simple olefins. Polyethylene and polyisoprene are important polyolefins.


polyol ester synthetic lubricant base, formed by reacting / fatty acids with a polyol (such as a glycol) derived from petroleum. Properties include good oxidation stability at high temperatures and low volatility. Used in formulating lubricants for turbines, compressors, jet engines, and auto­motive engines.

polystyrene - hard, clear thermoplastic polymer of styrene, colored and molded for a variety of applications, including structural materials. It is a good thermal and electrical insulator and, in the form of expanded foam, extremely buoyant.

positive crankcase ventilation (PCV) - refers to a system for eliminating blow-by gases from the crankcase. These gases are returned to the combustion chamber via the carburetor intake manifold. There the recirculated hydrocarbons are burned, thus reducing hydrocarbon emissions to the atmosphere. A PCV valve, operated by engine vacuum, controls the flow of gases from the crankcase. PCV systems have been standard equipment in all U.S. cars since 1963, replacing the simpler vent, or breather, that allowed crankcase vapors to be emitted to the atmosphere. See emissions (automotive).

positive displacement - direct increase in pressure by reducing the volume of the chamber in which a gas or liquid is confined. See compres­sor, pump.

pour point - lowest temperature at which an oil or distillate fuel is observed to flow, when cooled under conditions prescribed by test method ASTM D97. The pour point is 3°C (5°F) above the temperature at which the oil in a test vessel shows no movement when the container is held horizontally for five seconds. Pour point is lower than wax appearance point or cloud point. It is an indicator of the ability of an oil or distillate fuel to flow at cold operating temperatures.

pour point depressant additive used to lower the pour point of a petroleum product.

power - rate at which energy is used, or at which work is done. Power is commonly measured in terms of the watt (one joule per second) or horsepower (33,000 foot-pounds per minute, or 745.7 watts).

power factor - a ratio. It's the power in watts dissipated in an insulating medium divided by the product of effective voltage and current values in volt-amperes. It measures the tendency of an insulating oil, a dielectric, to allow current leakage. This is determined using the ASTM D924 test method. Such current leakage is called dielectric loss. The lower the power factor, the lower the dielectric loss. Determination of power factor can be used to indicate not only the inherent dielectric properties of an oil, but the extent of deterioration of a used oil, since oxidation products and other polar contaminants reduce dielectric strength, causing the power factor to rise. Power factor is related to dissipation factor.


powerforming - a patented catalytic reforming process.

ppb - parts per billion.

ppm - parts per million.

pre-ignition - ignition of a fuel-air mixture in an internal combustion engine (gasoline) before the spark plug fires. It can be caused by a hot spot in the combustion chamber or a very high compression ratio. Pre-ignition reduces power and can damage the engine. See knock.


pressure - force per unit area, measured in kilopascals (kPa) or pounds per square inch (psi). Standard atmospheric pressure at sea level is 101.3 kPa (14.7 psi), or one atmosphere. Gauge pressure, as indicated by a conventional pressure gauge, is the pressure in excess of atmospheric pressure. Absolute pressure is the sum of atmospheric and gauge pres­sures. Pressure is also expressed in terms of the height of a column of mercury that would exert the same pressure. One atmosphere is equal to 760 mm (29.9 in) of mercury.

pressure maintenance - method for increasing ultimate oil recovery by injecting gas, water, or other fluids into an oil reservoir, usually early in the life of the field in order to maintain or slow the decline of the reservoir pressures that force the oil to the surface.

pressure ratio (of a compressor) - the ratio (r) of the absolute discharge pressure to the absolute pressure at the inlet. This is mathematically expressed as: r= P2/P1, where P2 is the discharge pressure and P1 is the inlet pressure.

printing ink - a fluid or viscous compound consisting of a pigment finely dispersed in a vehicle, or varnish, that consists of resin, solvent, and additives. The pigment, which provides color and opacity, combines with the resin to form the hard film on the paper after the solvent carrier has disappeared. The petroleum solvent in ink can range from light, volatile material to heavy, high-boiling oil. This depends on the desired thickness and evaporation quality of the ink. Additives play multiple roles. They speed up or slow down drying and resist oxidation. They also improve scuff resistance and reduce viscosity. Furthermore, additives aid penetration and prevent sheet sticking. Paste ink is widely used in letterpress and lithographic processes. It has high viscosity and evaporates slowly with a high pigment density. Alternatively, liquid ink gets used in flexographic and gravure processes. It is thin, quick-drying, and holds less pigment. Lastly, screen ink is utilized in screen printing. It's denser than paste ink. See printing ink solvent, printing processes, tack.


printing ink solvent (ink oil) solvent or oil used to solubilize, or disperse, resins, pigments, and additives in ink formulation s; also used to adjust ink viscosity and drying characteristics. Selection of an ink solvent is based primarily on boiling range, viscosity, solvency, and molecular type (i.e., paraffinic, naphthenic). The solvent can range from a light, low­ boiling material (e.g., toluene} to heavy asphaltic material (commonly referred to as carbon black wetters). Important qualities in an ink solvent include the ability to be diluted (ability to hold a resin in suspension), good tack rise characteristics (control of ink stickiness), and low toxicity. An ink solvent that boils above 600°F is commonly referred to as an ink oil. See printing.


printing processes - techniques of applying ink to paper or other substrates. There are five basic printing methods: letterpress, flexography, gravure, lithography, and screen. Letterpress and flexography both uses inked raised type on plates wrapped around a rotating cylinder. Flexography differs from letter press in that the plate is flexible rubber, rather than metal. The two processes are used where print quality is not a primary consider­ation, such as newspapers, phonebooks, paper bags, and cardboard pack­ aging. Gravure, or intaglio, printing employs an etched or engraved plate that holds ink in tiny cells (thousands per square inch) below the plate surface. This technique produces the highest quality print and is preferred for photo reproduction. Lithography, or planography, uses a smooth plate created by a combination of photochemical and photomechanical processes that make the printing area ink receptive and the non-printing area water receptive. Lithography is also called offset printing because the image is transferred from the plate to a rubber roller or blanket, which prints the image. Lithography is gradually replacing letterpress in news­ paper and magazine printing. Screen printing uses a porous screen and a stencil that covers the non-printing areas. Ink is forced through the stencil openings onto the substrate. Screen printing is commonly used wherever a thick, durable ink coating is desired, such as T-shirts and outdoor posters. Petroleum-based ink solvents are commonly used in formulating the ink used in these various processes. See printing ink, printing ink solvent, tack.


process oil - oil that serves as a temporary or permanent component of a manufactured product. Aromatic process oils have good solvency characteristics; their applications include proprietary chemical formula­tions, ink oils, and extenders in synthetic rubbers. Naphthenic process oils are characterized by low pour points and good solvency properties; their applications include rubber compounding, printing inks, textile condi­tioning, leather tanning, shoe polish, rust proofing compounds, and dust suppressants. Paraffinic process oils are known for their low aromatic content and light color. They're used in furniture polishes, ink oils, and specific chemical formulations. See proprietary product.


process stream - general term applied to a partially finished petroleum product moving from one refining stage to another; less commonly applied to a finished petroleum product. See CAS Registry Numbers.


propane - gaseous paraffinic hydrocarbon (C3H8) present in natural gas and crude oil; also termed, along with butane, liquefied petroleum gas (LPG).


propellant - volatile gas or liquid which when permitted to escape from a pressurized container carries with it its particles or droplets of another material mixed or suspended in it. Propane and butane are common petroleum-derived propellants.

proprietary product - product with a unique formulation or other characteristics that distinguish it from competitive products. See commodity product.


propylene - flammable gas (CH3CHCH2), derived from hydrocarbon cracking; used in the manufacture of polypropylene plastics.

psi - pounds per square inch.

psia - pounds per square inch absolute, equivalent to the gauge pressure plus atmospheric pressure. See pressure.


pump - mechanism through which force is applied to a liquid. There are two basic categories of pumps: posi­tive displacement and cen­trifugal. Positive displace­ment pumps force liquid to flow in volumetric propor­tion to decreasing pump vol­ume. Hydraulic systems are a primary application, wherein the hydraulic fluid functions as the lubricant. Positive displacement pumps can be divided in to reciprocating and rotary. Recipro­cating pumps use pistons, plungers, or diaphragms to increase and de­crease volume. Rotary pumps use a rotating device (gear, screw, or vane) to force liquid from the pump. Centrifugal pumps, also called kinetic pumps, differ from positive displacement pumps in that they provide uniform (non-pulsing) flow and adjustable flow velocity. Movement is imparted to the liquid through centrifugal force created by a rotating impeller. There are two basic types of centrifugal pumps: radial flow and axial flow. In the former type, liquid enters the pump at the impeller's axis of rotation and is forced outward by vanes. In the latter type, a propeller or screw on a rotating shaft moves liquid in the axial direction of the shaft.


quality of steam - see saturated steam.


quenching - immersion of a heated manufactured steel part, such as a gear or axle, in a fluid to achieve rapid and uniform cooling. Petroleum oils are often used for this purpose. Quenching provides hardness superior to that possible if the heat-treated part were allowed to cool slowly in air. Marquenching is a slower cooling process that minimizes distortion and cracking. There are two types of marquenching: martempering and austempering; the latter is the slower process and helps improve ductility. See quenching oil.


quenching oil - also called heat treating oil; it is used to cool metal parts during their manufacture and is often preferred to water because the oil's slower heat transfer lessens the possibility of cracking or warping of the metal. A quenching oil must have excellent oxidation stability and thermal stability, and should yield clean parts, essentially free of residue. See quenching. In refining terms, a quenching oil is an oil introduced into high temperature vapors of cracked (see cracking) petroleum fractions to cool them.



radial flow pump - see pump.


radical - atom or group of atoms with one or more unpaired electrons. A group of atoms functioning as a radical act or as a single atom, remaining intact during a chemic al reaction.

raffinate - in solvent extraction, that portion of the oil which remains undissolved and is not removed by the selective solvent.


rail-flange grease- lubricant applied in minute quantities to the side surface of a train rail to mini­mize metal-to-metal contact between the wheel flange and rail flange. (The top of the rail must not be lubricated as this would impede the progress of the train.) The grease may be applied from an on­ board lubricator through nozzles located just in front of the locomotive wheels, or from wayside lubricators located at rail curves, where wheel-rail friction is greatest. A rail-flange grease must have excellent anti-wear properties, water resistance, and adherence to lubricated surfaces.

Ramsbottom carbon residue - see carbon residue.


R&O - rust and oxidation inhibited. A term applied to highly refined industrial lubricating oils formulated for long service in circulating lubrication systems, compressors, hydraulic systems, bearing housing, gear boxes, etc. The finest R&O oils are often referred to as turbine oils.


Rankine - see temperature scales.


rapeseed oil (blown rapeseed oil) fatty oil used for compounding petroleum oil. See compounded oil.


rate of shear - see shear rate.


RC asphalt - see cutback asphalt.


RCRA - See Resource Conservation and Recovery Act.


reaction diluent - a material (usually a light saturated hydrocarbon, e.g., pentane, hexane) that is used as a carrier for the polymerization catalyst in the manufacture of polyolefins (see polymer). The material must be very pure since impurities "poison" the catalyst or hinder the polymerization by reacting with the olefins.


Reaumur - see temperature scales.


reciprocating - back and forth movement, e.g., the movement of pistons in engines, reciprocating pumps, and compressors. See internal combustion engine.


reclaimed aggregate material (RAM) - reprocessed pavement materi­als containing no reusable binding agent such as asphalt.


reclaimed asphalt pavement (RAP) - reprocessed pavement materials containing asphalt and aggregate (e.g., pebbles, crushed stone, shells).

recycling of asphalt paving - the reprocessing of old asphalt paving and associated materials for reuse as paving. There are three basic methods of recycling. (1) Hot mix recycling combines reclaimed asphalt with new asphalt, recycling agents. It also includes fresh materials like crushed stone. This is done in a central plant to produce hot- mix paving mixtures. (2) cold mix recycling. Recombi­nation of reclaimed asphalt and aggregate materials either in place, or at a central plant to produce a cold mix. (3) surface recycling is a process in which the old asphalt pavement surface is heated in place. It's then scarified, remixed with new asphalt or recycling agents as necessary, re-laid, and rolled.

Redwood viscosity- method for determining the viscosity of petroleum products; it is widely used in Europe, but has limited use in the U.S. The method is like Saybolt Universal viscosity; viscosity values are reported as "Redwood seconds."

refined wax - low-oil-content wax, generally with an oil content of 1.0 mass percent or less, white in color, and meeting Food and Drug Admin­istration Standards for Purity and Safety. Refined waxes are suitable for the manufacture of drugs and cosmetics, for coating paper used in food packaging, and for other critical applications. Also called fully refined wax. See oil content of petroleum wax.


refining - series of processes for converting crude oil and its fractions to finished petroleum products. Following distillation, a petroleum frac­tion may undergo one or more additional steps to purify or modify it. These refining steps include thermal cracking, catalytic cracking, polymeriza­tion, alkylation, reforming, hydrocracking, hydroforming, hydrogenation, hydrogen treating. Also, hydrofining, solvent extraction, dewaxing, de­oiling, acid treating, clay filtration, and deasphalting. Refined lube oils may be blended with other lube stocks. Additives may be incorporated, to impart special properties. Refined naphthas may be blended with alkylates, cracked stock or reformates to improve octane number and other properties of gasolines.


reformate - product of the reforming process.

reforming - thermal or catalytic refining process in which the hydrocar­bon molecules of a naphtha are rearranged to improve its octane number; the resulting product is used in blending high-octane gasoline.


refractive index - ratio of the velocity of light at a specified wavelength in air to its velocity in a substance under examination. The refractive index of light-colored petroleum liquids can be determined by test method ASTM D1218, using a refractometer and a monochromatic light source. Refractive index is an excellent test for uniform composition of solvents, rubber process oils, and other petroleum products. It may also be used in combination with other simple tests to estimate the distribution of naphrhenic, paraffinic, and aromatic carbon atoms in a process oil.

refrigeration oil - lubricant for refrigeration compressors. It should be free of moisture to avoid reaction (hydrolysis) with halogenated refriger­ants (see halogen) and prevent freezing of water particles that could impede refrigerant flow. It should have a low wax content to minimize wax precipitation on dilution with the refrigerant, which could block capillary­ size passages in the circulating system.

Reid vapor pressure - see vapor pressure.


relative density - see specific gravity.


relative humidity - see humidity.


release agent- see mold lubricant.


Research Octane Number (RON) - see octane number.


reservoir - Geology: sub surface formation of porous, permeable rock (usually sandstone, lime­stone, or dolomite) containing oil or gas within the rock pores. A typical oil reservoir contains gas, oil, and water, which occupy the upper, middle, and lower regions of the reservoir, re­spectively. The flow of res­ervoir fluids from the rock to the borehole is driven by gas pressure or water pressure. See enhanced recovery, rotary drilling. Lubrication: primary lubricant repository in a lubrication system, e.g., crankcase, gear box.


residual fuel oil - see fuel oil.


residual odor - see bulk odor.


residuum - see bottoms.


resins - solid or semi-solid materials, light yellow to dark brown, composed of carbon, hydrogen, and oxygen. Resins occur naturally in plants, and are common in pines and firs, often appearing as globules on the bark. Synthetic resins, such as polystyrene, polyesters, and acrylics (see acrylic resin), are derived primarily from petroleum. Resins are widely used in the manufacture of inks, lacquers, varnishes, plastics, adhesives, and rubber. See plastisols and organosols.


Resource Conservation and Recovery Act (RCRA) - U.S. statute, administered by the EPA, intended to control the disposition of hazardous waste. The statute imposes strict management and procedural require­ments on generators and transporters of hazardous waste and on owners/ operators of hazardous waste treatment, storage, and disposal facilities. RCRA does not address abandoned or inactive hazardous waste sites (see Comprehensive Environmental Response and Liability Act).


rheology - study of the deformation and flow of matter in terms of stress, strain, temperature, and time. The rheological properties of a grease are commonly measured by penetration and apparent viscosity.


rheopectic grease grease that thickens, or hardens, upon being subjected to shear. The phenomenon is the opposite of thixotropy.


rich octane number - see lean and rich octane numbers.


ring oil - low-viscosity R&O oil for lubricating high-speed textile twister rings. It is normally light in color to prevent staining, and many are compounded with fatty oils to prevent wear under conditions of high­ speed start-up. See compounded oil.


ring oiler - simple device for lubricating a journal bearing. A metal ring rides loosely on the journal shaft and the lower part of the ring dips into a small oil reservoir. The reservoir is fed by a bottle-fed oiler. The rotation of the shaft turns the ring, which carries oil up to the point of contact with the shaft and into the bearing. Though not ordinarily considered a circulating lubrication system, the ring oiler is similar in principle and generally requires a long-life oil of the R&O type.

ring-sticking - freezing of a piston ring in its groove, in a piston engine or reciprocating compressor, due to heavy deposits in the piston ring zone. This prevents proper action of the ring and tends to increase blow-by into the crankcase and to increase oil consumption by permitting oil to flow past the ring zone into the combustion chamber. See engine deposits.


road octane number - see octane number.


road oil - a heavy petroleum oil, usually one of the slow-curing (SC) grades of liquid asphalt. See cutback asphalt.


rock drill lubricant - high-quality oil formulated to meet the special demands of rock drills and other pneumatic tools. Such a lubricant must have exceptional extreme pressure properties (see EP additive) to lubri­cate under the high-impact conditions of rock drill operation.

rock oil - see petroleum.


rolling contact bearing - see bearing.


rolling oil - oil used in hot- and cold-rolling of ferrous and non-ferrous metals to facilitate feed of the metal between the work rolls, improve the plastic deformation of the metal, conduct heat from the metal, and extend the life of the work rolls. Because of the pressures involved, a rolling oil may be compounded (see compounded oil) or contain EP additives. In hot rolling, the oil may also be emulsifiable (see emulsion). See aluminum rolling oil.


rotary bomb oxidation test - see bomb oxidation stability.


rotary compressor - see compressor.


rotary drilling - drilling method utilizing a rotating bit, or cutting element, fas­tened to and rotated by a drill pipe, which also pro­vides a passageway through which the drilling fluid or mud is circulated. Addi­tional lengths of drill stem are added as drilling progresses. See enhanced recovery, reservoir.


rotary pump- see pump.


RS asphalt - see emulsi­fied anionic asphalt.


rubber - see natural rub­ber, synthetic rubber, vul­canization.


rubber oil - any petro­leum process oil used in the manufacture of rubber and rubber products. Rubber oils may be used either as rubber extender oils or as rubber process oils. Rubber extender oils are used by the synthetic rubber manufacturer to soften stiff elastomers and reduce their unit volume cost while improving performance characteristics of the rubber. Rubber process oils are used by the manufacturer of finished rubber products (tires, footwear, tubing, etc.) to speed mixing and compounding, modify the physical properties of the elastomer, and facilitate processing of the final product. See rubber oil classification.


rubber oil classification - system of four standard classifications for rubber oils, based on content of saturated hydrocarbons, polar com­pounds, and asphaltenes, as described by ASTM D2226.

rubber swell - see seal swell.


rust inhibitor - type of corrosion inhibitor used in lubricants to protect the lubricated surfaces against rusting. see R&O.


rust preventive - compound for coating metal surfaces with a film that protects against rust; commonly used for the preservation of equipment in storage. The base material of a rust preventive may be a petroleum oil, solvent, wax, or asphalt, to which a rust inhibitor is added. A formulation consisting largely of a solvent and additives is commonly called a thin­ film rust preventive because of the thin coating that remains after evaporation of the solvent. Rust preventives are formulated for a variety of conditions of exposure, e.g., short-time "in-process" protection, indoor storage, exposed outdoor storage, etc.


SAE (Society of Automotive Engineers) organization responsible for the establishment of many U.S. automotive and aviation standards, including the viscosity classifications of engine oils and gear oils.

SAE Axle and Manual Transmission Gear Oil Viscosity Classification - automotive gear oil classification system developed by the Society of Automotive Engineers (SAE). The SAE 70W, 75W, 80W, and 85W viscosity grades are determined by the maximum cold temperature at which a viscosity of 150,000 cp is attained. For the SAE 90, 140, and 250 grades, minimum and maximum viscosities at 100°C establish the grade designations. Gear oil SAE viscosity grades should not be confused with engine oil SAE viscosity grades. See SAE engine oil viscosity classifica­tion.


SAE service classification - see API Engine Service Categories.

SAE engine oil viscosity classification - system developed by the Society of Automotive Engineers (SAE) to classify engine oils by viscosity grades. Oils are classified based on their measured viscosity at high temperature for single grade oils and at low and high temperatures for multi-grade oils. Multi-grades have a high viscosity index (V.I.) and therefore may fall into more than one SAE grade classification, e.g., SAE l0W-40, ("W" denotes suitability for winter, or cold weather use). Maximum cranking viscosities and pumping temperatures are defined to satisfy SAE low-temperature requirements. Low-temperature viscosity is measured at a different temperature for each grade. High shear viscosity is measured at 150°C under high-shear conditions that duplicate those experienced in the ring zone of an operating engine. See the SAE viscosity grade chart below.

sandstone - sedimentary rock usually consisting of grains of quartz cemented by lime, silica, iron oxide, or other materials. Petroleum deposits are commonly found in sandstone formations. See reservoir.

saponification - process of converting certain chemicals into soaps, which are the metallic salts of organic acids. It is usually accomplished through reaction of a fat, fatty acid, or ester with an alkali - an important process in grease manufacture.

saponification number - number of milligrams of potassium hydroxide (KOH) that combines with 1 gram of oil under conditions specified by test method ASTM D94. Saponification number is an indication of the amount of fatty saponifiable material in a compounded oil. Caution must be used in interpreting test results if certain substances - such as sulfur com­pounds or halogens - are present in the oil, since these also react with KOH, thereby increasing the apparent saponification number.

saturated hydrocarbon - hydrocarbon with the basic formula CnH(2n+2); it is saturated with respect to hydrogen and cannot combine with the atoms of other elements without giving up hydrogen. Saturates are more chemi­cally stable than unsaturated hydrocarbons.

saturated steam - The equilibrium condition at which the temperature of the steam is the same as that of the liquid water from which it is formed. Under this condition, steam containing no moist water particles is called "100% quality." If the temperature of the steam is higher (at the same pressure), as in a steam radiator, the quality drops, and the steam becomes wet, or condenses. At 50% quality, half of the weight represents water, the other half vapor. Saturated steam at atmospheric pressure has a temperature of 100°C (212°F).

Saybolt chromometer - see color scale.

Saybolt Furol viscosity - the efflux time in seconds required for 60 milliliters of a petroleum product to flow through the calibrated orifice of a Saybolt Purol viscometer, under carefully controlled temperature, as prescribed by test method ASTM D88. The method differs from Saybolt Universal viscosity only in that the viscometer has a larger orifice to facilitate testing of very viscous oils, such as fuel oil (the word "Purol" is a contraction of "fuel and road oils"). The Saybolt Purol method has largely been supplanted by the kinematic viscosity method. See viscosity. Saybolt seconds - see Saybolt Universal Viscosity.

Saybolt Universal Viscosity - the efflux time in Saybolt Universal Seconds (SUS) required for 60 milliliters of a petroleum product to flow through the calibrated orifice of a Saybolt Universal Viscometer, under carefully controlled temperature, as prescribed by test method ASTM D88. This method has largely been supplanted by the kinematic viscosity method. See Saybolt Purol viscosity, viscosity.

SBR - see styrene-butadiene rubber.

SC asphalt - see cutback asphalt.

scale wax - soft, semi-refined wax, distinguished from slack wax by having a gene rally lower oil content; usually derived from slack wax by extracting most of the oil from the wax. Used in candle manufacture, coating of carbon paper, and in rubber compounds to prevent surface cracking from sunlight exposure. See oil content of petroleum wax, wax (petroleum).


scavenger - a component of lead antiknock compounds that reacts with the lead radical to form volatile lead compounds that can be easily scavenged from the engine through the exhaust system. Also, an indi­vidual who collects used lubricating oils for some secondary use.

scoring - distress marks on sliding metallic surfaces in the form of long, distinct scratches in the direction of motion. Scoring is an advanced stage of scuffing. See four-ball method, Timken EP test.


screen printing - see printing processes.


scrubber oil - see absorber oil.


scuffing - localized stress marks on sliding metallic surfaces, appear­ing as a matte finished area rather than as individual score marks.


scuff resistance - property of a wax coating that enables it to with stand abrasion. Scuff resistance is an indication of the extent to which paper­ carton-coating machine operation affects the appearance of the coated carton. Poor scuff resistance of a wax can also causes excessive wax deposition on machine parts and adversely affect machine operations.

sealing strength - effectiveness of a coating wax in forming a tight, strong, heat-sealed package closure. See laminating strength.


seal oil - see mineral seal oil.


seal swell (rubber swell) - swelling of rubber (or other elastomer) gaskets, or seals, when exposed to petroleum, synthetic lubricants, or hydraulic fluids. Seal materials vary widely in their resistance to the effect of such fluids. Some seals are designed so that a moderate amount of swelling improves sealing action.

secondary production - see secondary recovery.


secondary recovery - restoration of an essentially depleted oil reservoir to production by injecting liquids or gases into the reservoir to flush out oil or to increase reservoir pressure. Also called secondary production. See enhanced recovery, tertiary recovery.

sett grease - any grease that changes from a fluid to a semifluid or plastic state after combination of the components, and often after packaging.

shale oil - see oil shale.


shear rate - rate at which adjacent layers of a fluid move with respect to each other, usually expressed as reciprocal seconds (also see shear stress). When the fluid is placed between two parallel surfaces moving relative to each other: she rate equals the relative velocity of the surface (meters/second) divided by the distance between the surfaces (meters).

shear stress - frictional force overcome in sliding one "layer" of fluid along another, as in any fluid flow. The shear stress of a petroleum oil or other Newtonian fluid at a given temperature varies directly with shear rate (velocity). The ratio between shear stress and shear rate is constant; this ratio is termed viscosity. The higher the viscosity of a Newtonian fluid, the greater the shear stress as a function of rate of shear. In a non­ Newtonian fluid - such as a grease or a polymer-containing oil (e.g., multi-grade oil) - shear stress is not proportional to the rate of shear. A non-Newtonian fluid may be said to have an apparent viscosity, a viscosity that holds only for the shear rate (and temperature) at which the viscosity is determined. See Brookfield viscosity.


SI (Systeme International, International System of Units) - metric ­based system of weights and measures adopted in 1960 by the 11th General Conference on Weights and Measures, in which 36 countries, including the U.S., participated. SI consists of seven base units. There are many derived units, each defined in terms of the base units: for example, the newton (N) - a unit of force- is defined by the formula kg x m/s2, and the joule (J), by the relations hip N x m. See metric system.


sidestream distillation fraction taken from any level of a distillation tower other than as overhead or bottoms.


sight fluid - transparent liquid in a sight-feed oiler through which the passage of the oil drops can be observed. The sight fluid must be immiscible with the oil. Water and glycerin are often used for this purpose. See mechanical lubricator.


silicate esters - class of synthetic lubricants, possessing good thermal stability and low volatility. Commonly used in military applications as high-temperature hydraulic fluids, weapons lubricants, and low-volatility greases.

silicone - generic term for a family of relatively inert liquid organo-siloxane polymers used as synthetic lubricants; properties include high viscosity index (V.I.), good high temperature oxidation stability, good hydrolytic stability and low volatility. Silicones generally have poor lubricity, how­ever. Applications include brake fluids, electric motors, oven and kiln preheater fans, automotive fans, plastic bearings, and electrical insulating fluids.

single-grade oil engine oil that meets only the high-temperature requirements of the SAE viscosity classification system. See SAE engine oil viscosity classification.


slack wax - a semi-refined wax, distinguished from scale wax by having a generally higher oil content. Slack waxes with oil content below 10 mass percent are used for manufacture of religious candles, as a feed stock for chlorination processes (see chlorinated wax), and in non -critic al paper­ making applications. Slack waxes with higher oil content are used in the manufacture of building materials, such as particle board. See oil content of petroleum wax, refined wax, wax (petroleum).


sleeve bearing - journal bearing. See bearing.


sliding bearing - see bearing.


sludge - in gasoline engines, a black emulsion of water, other combus­tion by-products, and oil fanned primarily during low-temperature engine operation. Sludge is typically soft but can be very hard. It plugs oil lines and screens and accelerates wear of engine parts. Sludge deposits can be controlled with a dispersant additive that keeps the sludge constituents suspended in the oil. See engine deposits.


slumping - ability of grease to settle to the bottom of a container and form a level surface. When being pumped from the bottom of a container, grease must slump rapidly enough toward the pump suction to maintain flow.

slushing oil - non-drying petroleum-based rust preventive used in steel mills to protect the surfaces of steel sheets and strips after rolling.

smoke point (of aviation turbo fuel) - maximum flame height obtain­ able in a test lamp without causing smoking, as determined by test method ASTM D1322. It is a measure of burning characteristics; the higher the numerical rating, the cleaner burning the fuel.


soap thickener - see grease.


Society of Automotive Engineers - see SAE.


Society of Tribologists and Lubrication Engineers - see STLE.


sodium soap grease - see grease.


SOD lead corrosion - test developed by Exxon to measure the corro­siveness of lubricating oils. A small lead panel of known weight and a copper panel (as catalyst) are attached to a spindle, which is immersed in a tube of the lubricant and rotated. Air is introduced at the bottom of the tube and allowed to bubble up through the sample. The weight loss by the lead panel after a specified period of time is a measure of the corrosiveness of the oil. See corrosion.


softening point (asphalt) - temperature at which the harder asphalts reach an arbitrary degree of softening; usually determined by the ring and ball test method, ASTM D36.

solids content - that portion of a protective coating material that remains on the surface after drying, often identified as non-volatiles.


soluble oil - emulsifiable cutting fluid.


solvent - compound with a strong capability to dissolve a given sub­ stance. The most common petroleum solvents are mineral spirits, xylene, toluene, hexane, heptane, and naphthas. Aromatic-type solvents have the highest solvency for organic chemical materials, followed by naphthenes and paraffins. In most applications the solvent disappears, usually by evaporation, after it has served its purpose. The evaporation rate of a solvent is very important in manufacture: rubber cements often require a fast-drying solvent, whereas rubber goods that must remain tacky during processing require a slower drying solvent. Solvents have a wide variety of in dust rial applications, including the manufacture of paints, inks, cleaning products, adhesives, and petrochemicals. Other types of solvents have important applications in refining. See printing ink solvent, solvent­ cutback, solvent extraction.


solvent-cutback - a petroleum product often used as a lubricant or rust-preventive. It's typically a heavy, asphaltic type diluted with a solvent.

solvent extraction refining process used to separate reactive compo­nents (unsaturated hydrocarbons) from lube distillates to im­prove the oil’s oxidation stability, viscosity index (V.I.), and response to additives. Commonly used extraction media (solvents) are phenol, N­ methyl pyrrolidone (NMP), furfural, liquid sulfur dioxide, and nitroben­zene. The oil and solvent are mixed in an extraction tower, resulting in the formation of two liquid phases: a heavy phase consisting of the undesir­able unsaturates (see hydrocarbon unsaturates) dissolved in the solvent, and a light phase consisting of high-quality oil with some solvent dissolved in it. The phases are separated, and the solvent recovered from each by distillation. The unsaturated portion, or extract, while undesirable in lubricating oils, is useful in other applications, such as rubber extender oils (see rubber oil) and plasticizer oils.

solvent neutral - high quality paraffin-base oil refined by solvent extraction.

solvent oil - see fluidizer.


sour crude crude oil containing appreciable quantities of hydrogen sulfide or other sulfur compounds, as contrasted to sweet crude.


sparging - see air sparging.


spark-ignition engine - see internal combustion engine.


specialty product- in the petroleum industry, typically any petroleum product other than fuels. In general, the term encompasses lubricants, lubricant base stocks, process oils, waxes, solvents, and asphalt.


specific gravity (relative density) - for petroleum products, the ratio of the mass of a given volume of product and the mass of an equal volume of water, at the same temperature. The standard reference temperature is 15.6°C (60°F). Specific gravity is determined by test method ASTM D1298: the higher the specific gravity, the heavier the product. Specific gravity of a liquid can be determined by means of a hydrometer, a graduated float weighted at one end, which provides a direct reading of specific gravity, depending on the depth to which it sinks in the liquid. A related measurement is density, an absolute unit defined as mass per unit volume - usually expressed as kilograms per cubic meter (kg/m3). Petroleum products may also be de­ fined in terms of API gravity (also determinable by ASTM D1298), the API gravity value, the lighter the material, or the lower its specific gravity.

specific heat - ratio of the quantity of heat required to raise the temperature of a substance one degree Celsius (or Fahrenheit) and the heat required to raise an equal mass of water one degree.

spectrographic analysis (elemental analysis) - tech­nique for detecting and quantifying in a used oil metallic elements resulting from wear, contamination, or additives. The oil sample is energized to make each element emit or absorb a quantifiable amount of energy, which indicates the element's concentration in the oil. See chroma­tography, ferrography, infrared analysis, particle count, spectroscopy.


spectroscopy - the study of electromagnetic spectra arising from either emission or absorption of radiant energy by various substances. See infrared analysis, spectrographic analysis.

speed factor - see dN factor.


spin finish - see fiber lubricant.


spindle oil - low-viscosity oil of high quality for the lubrication of high­ speed textile and metal-working (grinding) machine spindles. In addition to the rust and oxidation (R&O) inhibitors needed for prolonged service in humid environments, spindle oils are often fortified with anti-wear additives to reduce torque load and wear, especially at start-up.

spindle test - test to determine the performance life of a grease. Under test method ASTM D3336, a grease lubricated SAE No. 204 size ball bearing on a spindle, or shaft, is rotated at l0,000 rpm under light loads and elevated temperatures. The test continues until bearing failure or until completion of a specified number of hours of running time.

spiral bevel gear - see gear.


splash lubrication - simple method of lubrication in which a revolving part, such as a gear or a connecting rod, dips into an oil reservoir, such as a crankcase or gear box, and slings the lubricant to other parts of the machine. Surplus oil drips back into the reservoir. Automotive engines, reciprocating compressors, geared drives, chain drives, and reduction gears are examples of equipment lubricated wholly or partly by splash.

spray oil - see orchard spray oil.


spur gear - see gear.


squeeze lubrication - phenomenon that occurs when surfaces, such as two gear teeth, move toward each other rapidly enough to develop fluid pressure within the lubricant that will support a load of short duration. The lubricant's viscosity prevents it from immediately flowing away from the area of contact.

SS asphalt - see emulsified anionic asphalt.


SSF (Saybolt Furol seconds) - see Saybolt Furol viscosity.


SSU, SUS (Saybolt Universal seconds)- see Saybolt Universal Viscos­ity.


static electricity - accumulation of an electrical charge on a surface as a result of the rubbing together of nonconducting solids or liquids. The trapped static electricity may be released as a spark toward a nearby surface with a different charge potential. If the spark occurs in the presence of an ignitable mixture, such as a flammable concentration of hydrocarbon, vapors, or finely divided particles of dust in air, explosion and fire can result. This phenomenon is called electrostatic ignition. Many types of industrial activities can generate static electricity (e.g., non-conducting fluid flowing through pipes, pulverized materials passing through chutes or pneumatic conveyors, churning vats, moving vehicles). Care should be taken in the workplace to minimize static buildup and to keep ignitable mixtures away from areas where static may occur.

stationary source emissions - see emissions (stationary source).


statistical process control (SPC) - use of control charts to track and eliminate variables in repetitive manufacturing processes, to ensure that the product is of consistent and predictable quality. If a chart reveals only chance variations that are inherent in the system, the process is said to be in a state of "statistical control.” If the chart reveals variations traceable to changes in equipment, procedures or workers, the process is said to be "out of control.” Statistical process control is different from statistical quality control. The former supervises manufacturing process parameters. On the other hand, the latter oversees product quality parameters.

statistical quality control (SQC) - use of statistical techniques to demonstrate consistency in the quality of a product. The primary tool used is a quality control chart showing control limits and other relevant statistical information. See statistical process control.


steam cylinder oil - see cylinder oil.


steam turbine - see turbine.


stereo rubber elastomer with a highly uniform arrangement of repeating molecular units (stereo isomers) in its structure. Polybutadiene rubber and polyisoprene rubber are stereo rubbers.

stick-slip motion - erratic, noisy motion characteristic of some machine ways due to the starting friction encountered by a machine part at each end of its back-and-forth (reciprocating) movement. This undesirable effect can be overcome with a way lubricant, which reduces starting friction.

STLE (Society of Tribologists and Lubrication Engineers) - organi­zation intended to advance the knowledge and application of lubrication and related sciences. See tribology.


Stoddard solvent mineral spirits with a minimum flash point of 37.8°C (100°F), relatively low odor level, and other properties conform­ing to Stoddard solvent specifications, as described in test method ASTM D484. Though formulated to meet dry cleaning requirements, Stoddard solvents are widely used wherever this type of mineral spirits is suitable.

stoichiometric - the exact proportion of two or more substances that will permit a chemical reaction with none of the individual reactants left over. See combustion.


stoke - see viscosity.


straight-chain paraffin - see normal paraffin.


straight mineral oil - petroleum oil containing no additives. Straight mineral oils include such diverse products as low-cost once-through lubricants (see once-through lubrication) and thoroughly refined white oils. Straight mineral oils are used in certain aviation piston engines, although a pour depressant may be added (see pour point). Most high­ quality lubricants, however, contain additives.

straight tooth gear - see gear.


strike through - undesirable migration of wax or oil through a paper substrate. A commonly used term in paper laminating operations, but also encountered in partial impregnation of corrugated board with wax. In the printing industry, the term refers to migration of printing ink, formulated with oil or solvent, to the reverse side of the web before setting.

strong acid number - see neutralization number.


strong base number - see neutralization number.


structural stability - resistance of a grease to change in consistency when severely worked in service. Also called shear stability and me­chanical stability.


styrene - colorless liquid (C8H8) used as the monomer (see polymer) for polystyrene and styrene-butadiene rubber.


styrene-butadiene rubber (SBR) - general purpose synthetic rubber with good abrasion resistance and tensile properties. SBR can be greatly extended with oil without degrading quality. Applications include auto­ mobile tires and wire insulation. See extender, rubber oil.


sulfated ash - see ash content.


sulfonate hydrocarbon in which a hydrogen atom has been replaced with the highly polar (S020X) group, where X is a metallic ion or alkyl radical. Petroleum sulfonates are refinery by-products of the sulfuric acid treatment of white oils. Sulfonates have important applications as emulsi­fiers and chemical intermediates in petrochemical manufacture. Synthetic sulfonates can be manufactured from special feed stocks rather than from white oil base stocks. See polar compound.


sulfur - common natural constituent of petroleum and petroleum prod­ucts. While certain sulfur compounds are commonly used to improve the EP, or load-carrying, properties of an oil (see EP oil), high sulfur content in a petroleum product may be undesirable as it can be corrosive and create an environmental hazard when burned (see sulfur oxide). For these reasons, sulfur limitations are specified in the quality control of fuels, solvents, etc. Sulfur content can be determined by ASTM tests.

sulfur oxide - a significant atmospheric pollutant. It consists mainly of sulfur dioxide (SO2) and some sulfur trioxide (SO3). It is primarily emitted from fixed combustion sources, like furnaces and boilers. Sulfur oxides are formed whenever fuels containing sulfur are burned. S02 is also present in the air from natural land and marine fermentation processes. See emissions (stationary source), pollutants.


supercharger - device utilizing a blower or pump to provide air to the intake manifold of an internal combustion engine at pressures above atmospheric. Supercharging provides a greater air charge to the cylinders at high crankshaft speeds and at high altitudes, thereby boosting engine power without increasing engine size. Because supercharging maintains maximum intake charge, it offers advantages at high altitudes, where the atmosphere provides less oxygen. Some supercharger systems utilize after-cooling to further increase the density of the charge. The blower may be geared to the crankshaft. See volumetric efficiency.


Superfund - see Comprehensive Environmental Response, Compensa­tion and Liability Act.


Superfund Amendments and Reauthorization Act (SARA) - a U.S. statute. It's an amendment to the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). The Environmental Protection Agency (EPA) administers it. The statute defines industry and governmental responsibilities and require­ments for emergency planning and public information regarding hazard­ous chemicals. It establishes the public's "right-to-know" about SARA­ listed chemicals in the community and workplace. It requires emergency notification procedures, reporting of chemical inventories and toxic chemical release, and emissions inventories.

supertanker - oil tanker with capacity over 100,000 deadweight tons (dwt); also called Very Large Crude Carrier (VLCC). A supertanker with a capacity over 500,000 dwt is called an Ultra Large Crude Carrier (ULCC).

surface-active agent - chemical compound that reduces interfacial tension between oil and water and is thus useful as an emulsifier in cutting oils (see cutting fluid). Sodium sulfonates or soaps of fatty acids are commonly used for this purpose.

surface ignition - see after-running.


surfactant - surface-active agent that reduces interfacial tension of a liquid. A surfactant used in a petroleum oil may increase the oil's affinity for metals and other materials.

SUS - Say bolt Universal seconds. See Saybolt Universal viscosity.


susceptibility - the tendency of a gasoline toward an increase in octane number by addition of a specific amount of a particular lead alkyl anti-knock compound. See antiknock compound.


sweep (of a piston) - internal cylinder surface area over which a piston of a reciprocating compressor moves during its stroke. Total piston sweep is a consideration in the determination of oil-feed rates for some recipro­cating compressor cylinders.

sweet crude - crude oil containing little or no sulfur. See sour crude.


syneresis - loss of liquid component from a lubricating grease caused by shrinkage or rearrangement of the structure due to either physical or chemical changes in the thickener, a form of bleeding.


synlube - see synthetic lubricant.


synthetic gas - see synthetic oil and gas.


synthetic lubricant - lubricating fluid made by chemically reacting materials of a specific chemical composition to produce a compound with planned and predictable prop­erties; the resulting base stock may be supplemented with additives to improve specific properties. Many synthetic lubricants - also called synlubes - are derived wholly or primarily from pet­rochemicals; other synlube raw materials are derived from coal and oil shale or are lipo-chemicals (from animal and vegetable oils). Synthetic lubricants may be superior to petroleum oils in specific performance areas. Many exhibits higher viscosity index (V.I.), better thermal stability and oxidation stability, and low volatility (which reduces oil consumption). Most synlubes offer longer service life and, in some cases, better biodegradability than conventional lubes; consequently, they are increasingly being used in industrial and automotive applications. Indi­vidual synthetic lubricants offer specific outstanding properties: phos­phate esters, for example, are fire resistant, diesters have good oxidation stability and lubricity, and silicones offer exceptionally high V.I. Polyalphaolefins are versatile lubricants with low pour points, and excellent thermal and oxidation stability; they have good compatibility with petroleum lubricants and most seals used with petroleum lubricants. Most synthetic lubricants can be converted to grease by adding thickeners. Because synthetic lubricants are higher in cost than petroleum oils, they are used selectively where performance or safety requirements may exceed the capabilities of a conventional oil.

synthetic oil and gas - any oil or gas suitable as fuel, but not produced by the conventional means of pumping from underground reserves. Synthetic gas may be derived from coal, naphtha, or liquid petroleum gas (LPG); and synthetic oil may be derived from coal, oil shale, and tar sands.

synthetic rubber - any petrochemical-based elastomer. Like natural rubber, synthetic rubbers are polymers, consisting of a series of simple molecules, called monomers, linked together to form large chain-like molecules. The chain forms a loose coil that returns to its coiled form after it is extended. See under individual listings: bury/ rubber, ethylene­ propylene rubber, natural rubber, neoprene rubber, nitrite rubber, polybutadiene rubber, polyisoprene rubber, polymer, stereo rubber, sryrene-butadiene rubber, vulcanization.


synthetic turbo oil non-petroleum lubricant for aircraft gas turbines generally made from an ester base. It is characterized by high oxidation stability and thermal stability, good load-carrying capacity, and the extreme low volatility required to prevent excessive evaporation under wide operating temperature conditions.


systemic effect - toxic effect that is produced in any of the organs of the body after a toxicant has been absorbed into the bloodstream. See acute effect, chronic effect, health hazard.




tack - in printing inks, ink particle cohesion that resists separation on the rollers of a press. Inks generally exhibit tack rise (i.e., increased sticki­ness) during printing, which can result in splitting or picking (surface removal) of the paper. Tack rise can be controlled to desired levels by adding solvents with different boiling characteristics and of different molecular types. Isoparaffins and normal paraffins impart very low tack rise; naphthenics, intermediate tack rise; and aromatics, high tack rise. Tack can be measured with an inkometer in terms of the torque developed by a system of rotating ink-wet rollers. See printing processes, printing ink solvent.


tackiness agent additive used to increase the adhesive properties of a lubricant, improve retention, and prevent dripping and splattering.

Tag closed tester - apparatus for determining the flash point of petro­leum liquids having a viscosity below 5.8 centistokes (cSt) at 37.8°C (l00°F) and a flash point below 93°C (200°F), under test methods prescribed in ASTM D56. The test sample is heated in a closed cup at a specified constant rate. A small flame of specified size is introduced into the cup through a shuttered opening at specified intervals. The lowest temperature at which the vapors above the sample briefly ignite is the flash point. See Pensky-Martens closed tester.


Tag open cup - apparatus for determining the flash point of hydrocarbon liquids, usually solvents, having flash points between -17.8° and 168 °C (0° to 325°F), under test methods prescribed in ASTM D1310. The test sample is heated in an open cup at a slow, constant rate. A small flame is passed over the cup at specified intervals. The lowest temperature at which the vapors above the sample briefly ignite is the flash point. See Cleveland open cup.


Tag-Robinson colorimeter - see color scale.


tail-end volatility - see distillation test.


TAN - total acid number. See neutralization number.


TBN - total base number. See neutralization number.


technical white oil - see white oil.


TEL (tetraethyl lead) - see lead alkyl.


tempering - hardening or strengthening of metal by application of heat or by alternate heating and cooling.

tempering oil - oil used as a medium for heating metals to the tempering temperature to relieve stress and improve toughness and ductility.

temperature scales - arbitrary thermometric calibrations that serve as convenient references for temperature determination. There are two widely used thermometric scales based on the freezing and boiling point of water at a pressure of one atmosphere: the Fahrenheit (F) scale (32°= freezing, 212° = boiling) and the Celsius (C), or Centigrade, scale (0°= freezing, 100° = boiling). There are two scales where 0° equals absolute zero, with all molecular movement theoretically stopping. These are the Kelvin (°K) or Absolute (°A) and Rankine (°R) scales. They correspond to the Celsius and Fahrenheit scales, respectively. 0°K equals -273.16°C while 0°R equals -459.69°F. The four scales can be related to each other by the following formulas.

°C = 5/9 (°F-32)

°K = °C + 273.16

°F = 9/5 °C+32

°R = °F + 459.69

Another scale based on the thermometric properties of water is the Reaumur scale, in which the freezing point is set at zero degrees and the boiling point at 80 degrees. This scale has only limited application.

terpolymer- copolymer formed by the polymerization of three different monomers. An example of a terpolymer is EPDM rubber, made from ethylene, propylene, and a third monomer (usually a diolefin). See polymer.


tertiary recovery - any method employed to increase removal of hydrocarbons from a reservoir after secondary recovery methods have been applied.

tetraethyl lead (TEL) - see lead alkyl.


tetramethyl lead (TML) - see lead alkyl.


texture - that property of a lubricating grease which is observed when a small portion of it is compressed, and the pressure slowly released. Texture should be described in the following terms. Brittle - tends to rupture or crumble when separated. Buttery - separates in short peaks with no visible fibers. Long fiber - shows short break-off with evidence of fibers. Resilient - capable of withstanding moderate com­pression without permanent deformation or rupture. Stringy - tendency to form long, fine threads without any visible fiber structure.

thermal cracking - in refining, the breaking down of large, high boiling hydrocarbon molecules into smaller molecules in the presence of heat and pressure. See cracking.


thermal stability - ability to resist chemical degradation at high tem­peratures.

thermal value - see heat of combustion.


thin-film rust preventive - see rust preventive.


thixotropy- tendency of grease or other material to soften or flow when subjected to shearing action. Grease will usually return to its normal consistency when the action stops. The phenomenon is the opposite of that which occurs with rheopectic grease. Thixotropy is also an important characteristic of drilling fluids, which must thicken when not in motion so that the cuttings in the fluid will remain in suspension.

thread compound - heavy grease, or grease-like lubricant, used to facilitate assembly and disassembly of threaded connections; it lubricates, seals, prevents seizing and galling, and protects against rust and corrosion. Typical applications include oil well tubing, casing threads, and drill pipe joints; water, gas, steam, and drainage lines; nuts and bolts. See anti-seize compound.


threshold limit value (TLV)- see occupational exposure limit.


throttle plate - see carburetor.


time-weighted average (TWA) - atmospheric concentration of a sub­ stance, in parts per million by volume, measured over a seven or eight-hour workday and 40-hour work week.

Timken EP test - measure of the extreme-pressure properties of a lubricating oil (see EP oil). The test utilizes a Timken machine, which consists of a stationary block pushed upward, by means of a lever arm system, against the rotating outer race of a roller bearing, which is lubricated by the product under test. The test continues under increasing load (pressure) until a measurable wear scar is formed on the block. Timken OK load is the heaviest load that a lubricant can withstand before the block is scored (see scoring).


TLV (threshold limit value) - see occupational exposure limit.


TML (tetramethyl lead) - see lead alkyl.


Toluene aromatic hydrocar­bon (C6HsCH3) with good sol­vent properties; used in the manu­facture of lacquers and other in­dustrial coatings, adhesives, printing ink, insecticides, and chemical raw materials and as an octane booster in gasoline. Also called toluol. See antiknock com­ pounds.


toluol - see toluene.


torque fluid - lubricating and power-transfer medium for commercial automotive torque converters and transmissions. It possesses the low viscosity necessary for torque transmission, the lubricating properties required for associated gear assemblies, and compatibility with seal materials.

total acid number - see neutralization number.


total base number - see neutralization number.


Toxic Substances Control Act (TSCA) - U.S. statute, administered through the EPA. It is intended primarily to identify chemicals that may present "an unreasonable risk of injury to health or the environment" and to establish a mechanism to control the manufacture, distribution, and importation of harmful chemicals in commerce. TSCA requires compa­nies to conduct health effects tests; provide Pre-Manufacture Notification (PMN) for substances not listed on the EPA inventory; report health allegations; and develop and maintain production, use, and exposure data on listed substances. See CAS Registry Numbers.


transformer oil - see electrical insulating oil.


tribology- science of the interactions between surfaces moving relative to each other. Such interactions usually involve the interplay of two primary factors: the load, or force, perpendicular to the surfaces, and the frictional force that impedes movement. Tribological research on friction reduction has important energy conservation applications since friction increases energy consumption.

trimer - see polymerization.


TSCA - see Toxic Substances Control Act.


turbine - device that converts the force of a gas or liquid moving across a set of rotor and fixed blades into motion. There are three basic types of turbines: gas, steam, and hydraulic. Gas turbines are powered by the expansion of compressed gases gene rated by the combustion of a fuel. (See internal combustion engine). Some of the power thus produced is used to drive an air compressor, which provides the air necessary for combustion of the fuel. In a turbo-jet aircraft engine, the turbine's only function is to drive the compressor: the plane is propelled by the force of the expanding gases escaping from the rear of the engine. In other applications, however, the rotor shaft provides the driving thrust to some other mechanism, such as a propeller or generator. Thus, gas turbines power not only turbo-jet aircraft, but also turbo-prop aircraft, locomotives, ships, compressors, and small-to-medium-size electric utility generators. Gas turbine-powered aircraft present severe lubrication demands that are best met with a synthetic turbo oil. Steam turbines employ steam that enters the turbine at high temperature and pressure and expands across both rotating and fixed blades (the latter serving to direct the steam). Steam turbines, which power large electric generators, produce most of the world's electricity. Only the highest-quality lubricants can with­ stand the wet conditions and high temperatures associated with steam turbine operation. The term turbine oil has thus become synonymous with quality. Hydraulic turbines (water turbines) are either impulse type, in which falling water hits blades for buckets on the periphery of a wheel that turns a shaft, or reaction type, where water und er pressure emerges from nozzles on the wheel, causing it to turn. Hydraulic turbines can be used to produce electric power near reservoirs or river dams.

turbine oil - top quality rust- and oxidation-inhibited (R&O) oil that meets the rigid requirements traditionally imposed on steam-turbine lubrication. (See turbine). Quality turbine oils are also distinguished by good demulsibility, a requisite of effective oil-water separation. Turbine oils are widely used in other exacting applications for which long service life and dependable lubrication are mandatory. Such applications include circulating systems, compressors, hydraulic systems, gear drives, and other equipment.

turbo charger - a device utilizing engine exhaust to provide air to the intake manifold of an internal combustion engine at pressures above atmospheric. See volumetric efficiency.


turbo fuel (Jet Fuel) kerosene-type fuel used in gas-turbine-powered aircraft (see turbine). Important properties of a turbo fuel include clean and efficient burning. Also, the ability to provide adequate energy for thrust. And resistance to chemical degradation in storage or when used as heat transfer medium on the aircraft. Also, non-corrosiveness; ability to be trans­ferred and metered under all conditions. Volatility high enough for burning but low enough to prevent excessive losses from tank vents. And freedom from dirt, rust, water, and other contaminants. Turbo fuel has different properties than aviation gasoline, which fuels piston engine aircraft.

turbo oil - see synthetic turbo oil.


TWA - see time-weighted average.


two-stroke cycle - see internal combustion engine.


typical inspection - description of a particular property of a petroleum product, usually expressed as the result of a standard test procedure. The following are typical inspections are for a lubricant: viscosity, viscosity index, oxidation, flash point, pour point, wear, rust protection, etc.


Ultra Large Crude Carrier (ULCC) - see supertanker.


ultraviolet absorbance - measurement of the ultraviolet absorption of petroleum products, determined by standardized tests, such as ASTM D2008. Aromatics absorb more ultraviolet _light than do naphthenes and paraffins, and the amount of absorbance can be used as an indication of the number of aromatics in a product. Certain polynuclear aromatics (PNAs) are known carcinogens (cancer-causing substances), with peaks of absor­bance generally between 280 and 400 milli-microns. The Food and Drug Administration (FD A) has therefore imposed limits on the amount of ultraviolet absorbance at these wavelengths for materials classified as food additives. However, not all materials with ultraviolet absorbance at these wavelengths are carcinogenic.

undisturbed penetration - see penetration (grease).

United States Geological Survey - see USGS.

United States Pharmacopeia - see USP.

unleaded gasoline gasoline that derives its anti-knock properties from high octane hydrocarbons or from non-lead anti-knock compounds, rather than from a lead additive. Leaded gasoline is being phased out for environmental reasons. See lead alkyl.


unsaturated hydrocarbon hydrocarbon lacking a full complement of hydrogen atoms, and thus characterized by one or more double or triple bonds between carbon atoms. Hydrocarbons having only one double bond between adjacent carbon atoms in the molecule are called olefins; those having two double bonds in the molecule are diolefins. Hydrocarbons having alternating single and double bonds between adjacent carbon atoms in a benzene-ring configuration are called aromatics. Hydrocarbons with a triple bond between carbon atoms are called acetylenes. Unsatur­ated hydrocarbons readily attract additional hydrogen, oxygen, or other atoms, and are therefore highly reactive. See saturated hydrocarbon, hydrogenation.


unsulfonated residue (USR or R) - as defined in the ASTM D483 test, the percentage of the oil sample that did not react with normal sulfuric acid. The phytotoxicity of agricultural oils has been shown to increase with an unsulfonated residue content below 90%. An oil with an unsulfonated residue content of 92% minimum is required for spraying orchard crops in the leaf or bud state. Above that level, there appears to be little or no added advantage in terms of reduced toxicity. See orchard spray oil.


unworked penetration - see penetration (grease).


USDA H-1/H-2 lubricants - see H-1/H-2 lubricants.


USGS (United States Geological Survey) - USGS stands for United States Geological Survey, a bureau of the Department of the Interior. Its responsibilities encompass surveys and investigations related to U.S. topography and geology. It also surveys mineral and water resources. Furthermore, the USGS enforces departmental regulations relevant to oil, gas, and other mining activities.

USP (United States Pharmacopeia) - compendium of drugs, drug formulas, quality standards and tests published by the United States Phannacopeial Convention, Inc., which also publishes the NF (National Formulary). The purpose of the USP is to ensure drug uniformity and to maintain and upgrade standards of drug quality and purity, as well as establish packaging, labeling, and storage requirements. The USP in­cludes standards for white oils under two classifications: " Mineral Oil" for heavy grades, and "Mineral Oil Light" for lighter grades.


vacuum tower - see distillation.


valve beat-in - wear on the valve face or valve seat in internal combus­tion engines resulting from the pounding of the valve on the seat. Also called valve sink or valve seat recession.


vapor lock - disruption of fuel movement to a gasoline engine caused by excessive vaporization of gasoline. Vapor lock occurs when the fuel pump, which is designed to pump liquid, loses suction as it tries to move fuel vapor. The engine will usually stall, but in less severe cases may accelerate sluggishly or knock due to an excessively lean fuel mixture. Factors favoring vapor lock are high ambient temperatures, low ambient pressure, volatile gasoline, and vehicle designs where heat from the engine can create high fuel line temperatures. Automotive engines are more likely to experience vapor lock during an acceleration that follows a short shutdown period. Vapor lock problems are most likely to occur in the late spring on unseasonably warm days, before the more volatile winter grades of gasoline have been replaced by the less volatile spring and summer grades (see volatility). Vapor lock can also occur in other types of pumping systems where volatile liquids are being handled.

vapor pressure - pressure of a confined vapor in equilibrium with its liquid at a specified temperature; thus, a measure of a liquid's volatility. Vapor pressure of gasoline and other volatile petroleum products is commonly measured in accordance with test method ASTM D323 (Reid vapor pressure). The apparatus is essentially a double chambered bomb. One chamber, fitted with a pressure gauge, contains air at atmospheric pressure; the other chamber is filled with the liquid sample. The bomb is immersed in a 37.8°C (100°F) bath, and the resulting vapor pressure of the sample is recorded in pounds per square inch (psi). Reid vapor pressure is useful in predicting seasonal gasoline performance (e.g., higher volatility is needed in cold weather, and lower volatility in hot weather), as well as the tendencies of gasolines, solvents, and other volatile petroleum prod­ucts toward evaporative loss and fire hazard.

varnish - 1) a hard coating, similar to varnish, formed from oil oxidation products. This substance bakes onto pistons during high-temperature operation. Typical examples are automotive engines and industrial machinery. Varnish can accelerate cylinder wear. Varnish formation can be reduced with the use of a detergent-dispersant and an oxidation inhibitor in the oil. See engine deposits. 2) In ink format ion, varnish - composed of resin, solvent, and additives - is the vehicle to which pigment is added to make printing ink.


Very Large Crude Carrier (VLCC) - see supertanker.


V.I. - see viscosity index (V.I.).


V.I. (viscosity index) improver - see viscosity index (V.I.) improver.


viscometer - device for measuring viscosity; commonly in the form of a calibrated capillary tube through which a liquid is allowed to pass at a controlled temperature in a specified time period. See kinematic viscosity, Saybolt Universal Viscosity.


viscosimeter - see viscometer.


viscosity - measurement of a fluid 's resistance to flow. The common metric unit of absolute viscosity is the poise, which is defined as the force in dynes required to move a surface one square centimeter in area past a parallel surface at a speed of one centimeter per second, with the surfaces separated by a fluid film one centimeter thick. For convenience, the centipoise (cp) - one one-hundredth of a poise - is the unit customarily used. Laboratory measurements of viscosity normally use the force of gravity to produce flow through a capillary tube (viscometer) at a con­trolled temperature. This measurement is called kinematic viscosity. The unit of kinematic viscosity is the stoke, expressed in square centimeters per second. The more customary unit is the centistoke (cSt) - one hundredth of a stoke. Kinematic viscosity can be related to absolute viscosity by the equation:

cSt = cp + fluid density.

Apart from kinematic viscosity, there exist other ways to determine viscosity. These include Saybolt Universal viscosity and Saybolt Furol viscosity. Moreover, there are Engler viscosity and Redwood viscosity. These all help ascertain the viscosity of a substance. Since viscosity varies inversely with temperature, its value is meaningless unless the temperature at which it is determined is reported. See viscosity (asphalt), viscosity index, viscosity-temperature relationship, viscosity selection.


viscosity (asphalt) - determined by any of several ASTM test methods. Two common methods are ASTM D2170 and D2171. The former method measures kinematic viscosity, that is, viscosity under the force of gravity, by allowing a test sample to flow down a capillary tube (viscometer) at a temperature of 135°C (275°F); the viscosity is expressed in centistokes. The latter method measures absolute viscosity. The liquid, at a temperature of 60 °C (140°F), is drawn up a tube by applying a vacuum; the viscosity is expressed in poises. In both tests the viscosity is obtained by multiplying the flow time in seconds by the viscometer calibration factor. See penetra­tion (asphalt), viscosity.


viscosity grading (asphalt) - classification system for asphalt cement, defined in American Association of State Highway Transportation Offi­cials (AASHTO) Specification M 226, and based on tests for viscosity, flash point, ductility, purity, etc., as outlined in test method ASTMD 3381. There are standard grades, from softest to hardest: AC-2.5, AC-5 , AC- 10, AC- 20, AC-40. Asphalt cement is also classified by penetration grading. See viscosity (asphalt).


viscosity-gravity constant (VGC) - indicator of the approximate hy­drocarbon composition of a petroleum oil. As described in test method ASTM D2501, VGC is calculated from an equation, depending on the temperature at which viscosity is determined (VGC at 37.8°C [100°F]).


viscosity index (V.I.) - empirical, unit less number indicating the effect of temperature change on the kinematic viscosity of an oil. Liquids change viscosity with temperature, becoming less viscous when heated; the higher the V.I. of an oil, the lower its tendency to change viscosity with temperature. The V.I. of an oil - with known viscosity at 40°C and at 100°C- is determined by comparing the oil with two standard oils having an arbitrary V.I. of 0 and 100, respectively, and both having the same viscosity at l00°C as the test oil. The following formula is used, in accordance with test method ASTM D2270:

V.I. = (L-U) / (L-H) x 100

where L is the viscosity at 40°C of the 0-V.I. oil, H is the viscosity at 40°C of the 100-V.I. oil, and U is the viscosity at 40°C of the test oil. There is an alternative calculation, also in ASTM D2270, for oils with V.I.'s above 100. The V.I. of paraffinic oils is inherently high, but is low in naphthenic oils, and even lower in aromatic oils (often below0). The V.I. of any petroleum oil can be increased by adding a viscosity index improver. High­ V.I. lubricants are needed wherever relatively constant viscosity is re­quired at widely varying temperatures. In an automobile, for example, an engine oil must flow freely enough to permit cold starting but must be viscous enough after warm-up to provide full lubrication (see multi-grade oil). Similarly, in an aircraft hydraulic system, which may be exposed to temperatures above 38°C at ground level and temperatures below -54 °C at high altitudes, consistent hydraulic fluid performance requires a high viscosity index.

viscosity index (V.I.) improver - lubricant additive, usually a high­ molecular weight polymer, that reduces the tendency of an oil to change viscosity with temperature. Multi-grade oils, which provide effective lubrication over a broad temperature range, usually contain V.I. improv­ers. See viscosity index.


viscosity selection - selecting a lubricant of the proper viscosity is based on three operating factors: speed, temperature, and load. • The faster the parts move, the easier it is to maintain full-fluid-film lubrication; therefore, a heavier load can be carried with a lighter oil. Also, higher speeds increase fluid friction, resulting in power loss; such friction is less with a low-viscosity oil. Conversely, slow-moving parts require a heavier oil, since a full-fluid film is more difficult to maintain at low speeds. High operating temperatures cause an oil to thin out (see viscosity­ temperature relationship); a high-viscosity oil is needed to compensate for this effect. At low ambient temperatures, an oil tends to thicken, which calls for a low-viscosity oil that will flow at cold temperatures. If temperature varies substantially, an oil with a high viscosity index should be considered (see multi-grade oil). High loads tend to squeeze the oil out of the bearing, which calls for the greater film strength of a high- viscosity oil (see lubricity). In summary, high speed/low­ temperature/low-pressure conditions call for a low-viscosity oil; low speed/high-temperature/high-pressure conditions call for a high viscosity oil. The best general practice is to use the lightest oil possible to minimize power loss.

viscosity-temperature relationship - the way the viscosity of a given fluid varies inversely with temperature. Because of the math­ematical relationship that exists between these two variables, it is possible to predict graphically the viscosity of a petroleum fluid at any temperature within a limited range if the viscosities at two other temperatures are known. The charts used for this purpose are the ASTM Standard Viscosity­ Temperature Charts for Liquid Petroleum Products, available in 6 ranges. If two known viscosity-temperature points of a fluid are located on the chart and a straight line drawn through them, other viscosity-temperature values of the fluid will fall on this line; however, values near or below the cloud point of the oil may deviate from the straight-line relationship.

VM&P Naphtha - Varnish Makers and Painters Naphtha; term for a naphtha commonly used as a solvent in paints and varnishes.

VOC - see volatile organic compound.


volatile organic compound (VOC) - any organic compound that reacts with nitrogen oxides in the presence of sunlight to form ozone, a major component of photochemical smog. VOCs are released from both natural and man-made sources (e.g., trees, automobiles). Automobile VOC emis­sions can be reduced by lowering gasoline vapor pressure, improving combust ion efficiency, and using catalytic converters to trap exhaust emissions. See emissions (automotive).


volume percent - see weight percent.

volatility - expression of evaporation tendency. The more volatile a petroleum liquid, the lower its boiling point and the greater its flammabil­ity. The volatility of a petroleum product can be precisely determined by tests for evaporation rate; also, it can be estimated by tests for flash point and vapor pressure, and by distillation tests.


volumetric efficiency - ratio of the weight of air drawn into the cylinder of an operating internal combustion engine to the weight of air the cylinder could hold at when the piston is at the bottom of the stroke and the valves are fully closed. Any restriction of air flow into the cylinder reduces volumetric efficiency, which, in turn, reduces power output. The volumetric efficiency of an automotive engine is usually slightly more than 80% at about half the rated speed of the engine, then decreases considerably at higher speed, thus limiting the power output of the engine. The air charge to the cylinder can be increased at high speeds by means of supercharging. See supercharger.


vulcanization (curing) - application of heat to convert rubber articles to their finished form. The process causes chemical bonds to form between adjacent molecules (cross-linking) through some reactive agent, such as sulfur or peroxides; the more cross-linking, the harder the finished rubber will be.


wash oil - see absorber oil.


water content of oil - see crackle test, Karl Fischer Method.


wax (petroleum) - any of a range of relatively high molecular weight hydrocarbons (approximately C16 to C50), solid at room temperature, derived from the higher boiling petroleum fractions. There are three basic categories of petroleum-derived wax: paraffin (crystalline), micro-crystal­ line and petrolatum. Paraffin waxes are produced from the lighter lube oil distillates, generally by chilling the oil and filtering the crystallized wax; they have a distinctive crystalline structure, are pale yellow to white (or colorless), and have a melting point range between 48°C (118°F) and 71°C (160°F). Fully refined paraffin waxes are dry, hard, and capable of imparting good gloss. • Microcrystalline waxes are produced from heavier lube distillates and residua (see bottoms) usually by a combination of solvent dilution and chilling. They differ from paraffin waxes in having poorly defined crystalline structure, darker color, higher viscosity, and higher melting points ranging from 63°C (145°F) to 93°C (200°F). The microcrystalline grades also vary much more widely than paraffins in their physical characteristics: some are ductile, and others are brittle or crumble easily. Both paraffin and microcrystalline waxes have wide used in food packaging, paper coating, textile moisture proofing, candle-making, and cosmetics. Petrolatum is derived from heavy residual lube stock by propane dilution and filtering or centrifuging. It is microcrystalline in character and semi-solid at room temperature. There are also heavier grades for industrial applications, such as corrosion preventives, carbon paper, and butcher's wrap. Traditionally, the terms slack wax, scale wax, and refined wax were used to indicate limitations on oil content. Today, these classifications are less exact in their meanings. This is true especially in the distinction between slack wax and scale wax. For further information relating to wax, see blocking point, chlorinated wax, gloss. Also includes laminating strength, melting point of wax, oil content of petroleum wax, paraffin wax, petrolatum. Also includes refined wax, scale wax, scuff resistance, sealing strength, slack wax, strike-through.


wax appearance point (WAP) - temperature at which wax begins to precipitate out of a distillate fuel, when the fuel is cooled under conditions prescribed by test method ASTM D3117. WAP is an indicator of the ability of a distillate fuel, such as diesel fuel, to flow at cold operating temperatures. It is very similar to cloud point.


way - longitudinal surface that guides the reciprocal movement of a machine part. See stick-slip motion, way lubricant.


way lubricant - lubricant for the sliding ways of machine tools such as planers, grinders, horizontal boring machines, shapers, jig borers, and milling machines. A good way lubricant is formulated with special frictional characteristics designed to overcome the stick-slip motion associated with slow-moving machine parts.

weed killer pesticide product, often derived from petroleum, used for destroying weeds by direct application to the plants. "Selective" weed killers are those that, when applied in accordance with instructions, are not destructive to specified crops. Non-selective weed killers kill all vegeta­tion. See agricultural oil.


weight percent - the amount of any component of a substance, expressed as a percentage of the substance's total weight, equivalent in value to mass percent. Weight percent is generally a more accurate measurement than volume percent since volume varies with temperature.

weld point - the lowest applied load in kilograms at which the rotating ball in the Four Ball EP test either seizes and welds to the three stationary balls, or at which extreme scoring of the three balls results. See four-ball method.


wellbore - see borehole.


wellhead - the point at which oil and gas emerge from below ground to the surface; also, the equipment used to maintain surface control of a well.

wet gas - natural gas containing a high proportion of hydrocarbons that are readily recoverable from the gas as liquids. See natural gas liquids.


white oil - highly refined straight mineral oil, essentially colorless, odorless, and tasteless. White oils have a high degree of chemical stability. The highest purity white oils are free of unsaturated components (see unsaturated hydrocarbon) and meet the standards of the United States Phannacopeia (USP) for food, medicinal, and cosmetic applications. White oils not intended for medicinal use are known as technical white oils and have many industrial applications including textile, chemical, and plastics manufacture where their good color, non-staining proper­ties, and chemical inertness are highly desirable.

wick-feed oiler - see oiler.


wide cut - see distillation test.


wildcat - exploratory oil or gas well drilled in an area not previously known to be productive.

wire rope - sturdy cable consisting of wire strands (often of high carbon steel) usually wound around a core of steel, plastic, or vegetable fiber (e.g., sisal). Steel and plastic cores provide greater strength; fiber cores provide greater flexibility. Wire rope has a broad range of uses. These uses include overhead cranes, elevators, and ski lifts. Lubrication is crucial for wire rope. It reduces friction among wires and between the core and nearby wires. It also diminishes friction between the rope and coarse external surfaces. Moreover, the lubricant should protect against corrosion.


wood alcohol - see methanol.


worked penetration - see penetration (grease).


workover - well that has been put back into production following remedial actions (such as deepening, clearing, acidizing) to restore or increase production.

worm gear - see gear.



xylene - aromatic hydrocarbon, C8H10, with three isomers plus ethylbenzene. It is used as a solvent in the manufacture of synthetic rubber products, printing inks for textiles, coatings for paper, and adhesives, and serves as a raw material in the chemical industry.


yield point - the minimum force required to produce flow of a plastic material. See plasticity.


ZDDP (zinc dialkyl dithiophosphate or zinc diaryl dithiophosphate) - widely used as an anti-wear additive in engine oils to protect heavily loaded parts, particularly the valve train mechanisms (such as the camshaft and cam followers) from excessive wear. It is also used as an anti-wear agent in hydraulic fluids and certain other products. ZDDP is also an effective oxidation inhibitor. Oils containing ZDDP should not be used in engines that employ silver alloy bearings. All car manufacturers now recommend the use of dialkyl ZDDP in engine oils for passenger car service.

ZN/P curve - general graphic representation of the equation: µ = (f) ZN/P, where µ (the coefficient of friction in a journal bearing) is a function (f) of the dimensionless parameter ZN/P, (viscosity x speed) / pressure. This is the fundamental lubrication equation, in which the coefficient of friction is the friction per unit load, Z the viscosity of the lubricating oil, the rpm of the journal, and the pressure (load per unit area) on the bearing. The ZN/P curve illustrates the effects of the three variables (viscosity, speed, and load) on friction and, hence, on lubrication. See boundary lubrication, full-fluid-film lubrication.

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