Lubricating Glossary of Terms
American Automobile Manufacturers Association consisting of Chrysler, Ford Motor Company and General Motors. Headquartered in Detroit, Michigan, AAMA proposes lubricant standard classifications and specifications for the U.S. automobile industry.
The amount of free acid in any substance.
An agent used for imparting new or for improving existing characteristics of lubricating oils or greases.
Additive Treat Level
The total percentage of all additives in an lubricating oil or grease.
Abbreviation for American Gear Manufacturers Association.
The incorporation of air in the form of bubbles as a dispersed phase in the bulk liquid. Air may be entrained in a liquid through mechanical means and/or by release of dissolved air due to a sudden change in environment. The presence of entrained air is usually readily apparent from the appearance of the liquid (ex: bubbly, opaque, etc.) while dissolved air can only be determined by analysis.
In chemistry, any substance having marked basic properties. In its restricted and common sense, the term is applied only to hydroxides of ammonium, lithium, potassium, and sodium. They are soluble in water. They have the power to neutralize acids and to form salts with them and to turn red litmus blue. In a more general sense, the term is also applied to the hydroxides of the so-called alkaline earth metals-barium, calcium and strontium.
Almen EP Lubricant Tester
A journal bearing machine used for determining the load-carrying capacity or extreme pressure properties of gear lubricants.
The minimum temperature for complete miscibility of equal volumes of aniline and the sample under test. ASTM Method D-611 describes procedures for determining aniline point and mixed aniline point of petroleum products and hydrocarbon solvents. A product of high aniline point will be low in aromatics and naphthenes and, therefore, high in paraffins. Aniline point is often specified for spray oils, cleaning solvents, and thinners, where effectiveness depends upon aromatic content. In conjunction with API gravity, the aniline point may be used to calculate the net heat of combustion of aviation fuels.
An additive used for controlling foam.
A type of bearing employing rollers or balls. They are now usually called rolling bearings.
Resistance to detonation or pinging in spark-ignition engines.
A chemical agent added to gasoline, lubricating oil, etc., to inhibit oxidation.
American Petroleum Institute.
API Engine Service Classification System
Classifications and designations for lubricating oils for automotive engines developed by API in conjunction with SAE and ASTM.
An arbitrary scale expressing the gravity or density of liquid petroleum products. The measuring scale is calibrated in terms of degrees API. It may be calculated in terms of the following formula:
Deg API = 141.5 – 131.5 (sp gr 60°F/60°F)
The ratio of shear stress to rate of shear of a non-Newtonian fluid such as lubricating grease, calculated from Poiseuille’s equation and measured in poises. The apparent viscosity changes with changing rates of shear and temperature and must, therefore, be reported as the value at a given shear rate and temperature (ASTM Method D-1092).
Derived from, or characterized by, the presence of the benzene ring.
The percent by weight of residue left after combustion of a sample of a fuel oil or other petroleum oil; it is usually determined in the United States by ASTM Method D-482.
Black to dark-brown solid or semisolid cementitious material which gradually liquefies when heated and in which the predominating constituents are bitumens. These occur in the solid or semisolid form in nature; are obtained by refining petroleum; or are combinations with one another or with petroleum or derivatives thereof.
Essentially composed of, or similar to, asphalt; frequently applied to lubricating oils derived from crude oils which contain asphalt.
American Society for Testing and Materials, which Committee D-2 is on Petroleum Products and Lubricants.
Apparatus widely used for determining the color of lubricating oil. It is described in ASTM Method D-1500. The color so determined is known as ASTM Color.
ASTM Gum Test
1. An analytical method for determining the amount of existing gum in a gasoline by evaporating a sample from a glass dish on an elevated-temperature bath with the aid of circulating air.
2. Any gum test carried out in accordance with an ASTM gum test procedure. (ASTM Method D-381 and ASTM Method D-525 are generally used in the United States for the determination of gum in motor gasoline.)
ASTM Melting Point
The temperature at which wax first shows a minimum rate of temperature change; also known as the English melting point.
The spontaneous ignition, and the resulting very rapid reaction, of a portion or all of the fuel-air mixture in an engine. The flame speed is many times greater than that which follows normal spark ignition. The noise associated with it is called knock.
A unit of liquid measure comprised of 42 gallons. Used to measure quantities of crude oil, gasoline and fuel oils.
Any quantity of material handled or considered as a unit in processing.
The mineral montmorillonite, a magnesium-aluminum silicate. Used as a treating agent, as a component of drilling mud, and in greases.
The process of chemical breakdown or transformation of a substance caused by biological systems (micro-organisms and their enzymes).
The color of an oil by reflected light when this differs from its color by transmitted light. For certain purposes the trade has preferred oils of yellowish-green rather than bluish-green bloom. This demand can be met by special processing.
The temperature at which a substance boils or is converted into vapor by bubbles forming within the liquid; it varies with pressure.
A state of lubrication existing when conditions of bearings, design, feed, load, and method of application of the lubricant do not permit the formation of a separating lubricant film by hydrodynamic action. Under these conditions, adsorption of the lubricant or of some of the active components of the lubricant upon the bearing surface, or the formation of low-shear-strength chemical compounds by the reaction of the components of the lubricant with the bearing surfaces, reduces the metallic contact and determines the character of the frictional resistance.
Refined, high viscosity lubricating oils usually made from residual stocks by suitable treatment, such as a combination of acid treatment or solvent extraction with dewaxing or clay finishing.
British Thermal Unit (BTU)
The quantity of heat required to raise, by 1°F, the temperature of water at its maximum density (39.2°F).
Coordinating European Council, which test method CEC L-33-A93 (formerly CEC L-33-T82) is widely used to determine the primary biodegradation of lubricants.
The unit of kinematic viscosity.
Cetane Number (Calculated)
The cetane number of distillate fuels as estimated from the API gravity and midboiling point by using a formula given in Appendix II of ASTM Method D-975. This estimate is used if a standard test engine is not available, or if the sample is too small for an engine test.
Cetane Number (Test Method)
The percentage by volume of normal cetane, in a blend with heptamethylnonae (HMN), which matches the ignition quality of the fuel when compared by the procedure specified in ASTM Method D-613.
Cetane Number Improver
A substance which, when added to a diesel fuel, has the effect of increasing its cetane number. In this class are nitro alkanes, nitrates, nitro carbonates, and peroxides.
An approximation of cetane number based on API gravity and mid-boiling point of a fuel.
Coordinating Fuel and Equipment Research Committee, composed of engine-manufacturing, petroleum-refining, petroleum-consuming, university, government, and other technical men who supervise cooperate testing and study of engine fuels for the Coordinating Research Council, Inc.
1. The phenomenon observed among gear lubricants and greases when they thicken, due to cold weather or other causes, to such an extent that a groove is formed through which the part to be lubricated moves without actually coming in full contact with the lubricant. 2. A term used in percolation filtration; may be defined as a preponderance of flow through certain portions of the clay bed.
With respect to a petroleum oil, the temperature at which paraffin wax or other solid substances begin to crystallize or separate from the solution, imparting a cloudy appearance to the oil when the oil is chilled under prescribed conditions. These conditions are described in ASTM Method D 97.
A factor in the identification, rather than in the quality rating of a petroleum product – except where staining or appearance are considerations. See specific types of color under alphabetic listing.
A lubricating grease thickened by a complex soap consisting of a normal soap and a complex agent. The use of soap complexes gives products which have higher softening points than similar lubricants made from normal soaps.
The addition of fatty oils and similar materials to lubricants to impart special properties. Lubricating oils to which such materials have been added are known as compounded oils.
Coordinating Research Council, Inc. (CRC)
An organization supported jointly by the American Petroleum Institute and the Society of Automotive Engineers, and which administers the work of CFR (see page 167) and other committees pertaining to correlation of test work on fuels, lubricants, engines, etc.
Copper Strip Corrosion (ASTM D 130)
The gradual eating away of metallic surfaces as the result of oxidation or other chemical action. It is caused by acids or other corrosive agents.
The gradual eating away of metallic surfaces as the result of oxidation or other chemical action. It is caused by acids or other corrosive agents.
Centistoke, the unit of kinematic viscosity.
The mass of a unit of volume of a substance.
A lubricating oil possessing special sludge-dispersing properties for use in internal-combustion engines. These properties are usually conferred on the oil by the incorporation of special additives. Detergent oils hold sludge particles in suspension and thus promote engine cleanliness.
A measure of the adequacy of insulating materials for the electrical stresses they are intended to resist. Testing of electrical insulating oils of petroleum origin for use in cable, transformer, oil circuit breakers, and similar apparatus is usually done in the United States by ASTM Method D 877.
An expression for the ignitability of a fuel relative to its aniline point:
Diesel index = aniline point (F) times API gravity 100
A synthetic lubricating fluid made from esters; also called ester oil.
A dispersing agent, compatible with a carrier fluid, which holds a very finely divided third substance in a dispersed state in the carrier fluid.
Any of a wide range of products produced by distillation as distinct from residuals.
In general, the dropping point is the temperature at which the grease passes from a semisolid to a liquid state under the conditions of the test. The method is useful in identifying the grease as to type and for establishing and maintaining benchmarks for quality control. The results should be considered to have only limited significance with respect to service performance as dropping point is a static test.
Solid material placed between two moving surfaces to prevent metal-to-metal contact, thus reducing friction and wear. Such materials are especially useful in the region of semifluid and boundary lubrication, and for lubrication under special conditions of extremely high or low temperature where the usual lubricants are inadequate. They may be applied in the form of a paste or solid stick, or by spraying, dipping, or brushing in an air-drying carrier which evaporates leaving a dry film. Some examples are graphite, molybdenum disulfide, boron nitride, and certain plastics such as tetrafluorethylene resins. Often mixtures of such solid lubricants are used.
Lubrication modified to take into consideration the elastic properties of the bearing material and the viscosity increase of the lubricant under concentrated load.
A substance used to promote or aid the emulsification of two liquids and to enhance the stability of the emulsion.
Abbreviation for extreme pressure.
An additive introduced into a lubricant to impart load carrying or anti-weld qualities, etc.
Extreme-pressure lubricant; any of the lubricating oils or greases which contain a substance or substances specifically introduced to prevent metal-to-metal contact in the operation of highly loaded gears. In some cases, this is accomplished by the substances reacting with the metal to form a protective film.
An animal or vegetable oil which will combine with an alkali to saponify and form a soap.
A grease with a distinctly fibrous structure, which is noticeable when portions of the grease are pulled apart.
Any substance, such as talc, mica, or various powders, which may be added to a grease to make it heavier in weight or consistency, but which serves no useful function in making the grease a better lubricant. (Editor’s note: Such fillers may also be added to certain lubricating oils or other lubricants.)
The property of an oil which enables it to maintain an unbroken film on lubricated surfaces under operating conditions, where otherwise there would be scuffing or scoring of the surfaces.
The lowest temperature at which, under specified conditions in standardized apparatus, a petroleum product vaporizes sufficiently rapidly to form above its surface an air-vapor mixture which burns continuously when ignited by a small flame.
The lowest temperature at which vapors arising from the oil will ignite momentarily (i.e., flash) on application of a flame under specified conditions. 1. Cleveland open-cup (COC) tester is used for the determination of flash and fire points of all petroleum products flashing above 175°F, with the exception of fuel oils. Usually used as prescribed in ASTM Method D-92. 2. Pensky-Martens tester is used for the determination of the flash point of mobile liquids below 175°F, with the exception of fuel oils.
The temperature at which wax or solids separate in an oil.
An agglomeration of gas bubbles separated from each other by a thin liquid film which is observed as a persistent phenomenon on the surface of a liquid.
This name is frequently used to describe either of two similar laboratory machines, the Four-Ball Wear Tester and the Four-Ball EP Tester. These machines are used to evaluate a lubricant’s anti-wear qualities, frictional characteristics or load carrying capabilities. It derives its name from the four 1/2 inch steel balls used as test specimens. Three of the balls are held together in a cup filled with lubricant while the fourth ball is rotated against them.
A German gear test for evaluating EP properties.
Fuel mixture of 90% gasoline and 10% ethyl alcohol (ethanol).
A lubricant composed of a lubricating fluid, thickened with soap or other material to a solid or semisolid consistency.
Heat Transfer Oil
A medium used for the transfer of heat at temperature levels above that of steam. Probably the most widely used medium is a high-boiling petroleum fraction, usually in the gas oil range.
Humidity Cabinet Test
A test used to evaluate the rust-preventing properties of metal preservatives under conditions of high humidity (ASTM Method D-1748).
A compound containing only hydrogen and carbon. The simplest hydrocarbons are gases at ordinary temperatures; but with increasing molecular weight, they change to the liquid form and, finally, to the solid state. They form the principal constituents of petroleum.
Hydrodynamic (Fluid Film) Lubrication
A descriptive term. An oil film in a bearing generates a pressure equal to the load on the bearing, and this pressure raises the moving shaft from the bearing by a wedge like action.
The chemical addition of hydrogen to a material. In non-destructive hydrogenation, hydrogen is added to a molecule only if, and where, unsaturation with respect to hydrogen exists. In destructive hydrogenation, the operation is carried out under conditions which result in rupture of some of the hydrocarbon chains (cracking); hydrogen is added where the chain breaks have occurred.
Gear in which the pinion axis intersects the plane of the ring gear at a point below the ring-gear axle and above the outer edge of the ring gear, or above the ring-gear axle and below the outer edge of the ring gear.
A substance, the presence of which, in small amounts, in a petroleum product prevents or retards undesirable chemical changes from taking place in the product, or in the condition of the equipment in which the product is used. In general, the essential function of inhibitors is to prevent or retard oxidation or corrosion.
An oil used in circuit breakers, switches, transformers, and other electrical apparatus for insulating, cooling, or both. In general, such oils are well-refined petroleum distillates of low volatility, with high resistance to oxidation and sludging.
Abbreviation for International Standards Organization.
The ratio of the absolute viscosity to the density at the temperature of the viscosity measurement. The metric units of kinematic viscosity are the stoke and centistoke, which correspond to the poise and centipoise of absolute viscosity.
An animal oil prepared from the fat of swine. Such oils are compounded with mineral oils to yield lubricants of special properties, especially cutting oils.
Liquefied Petroleum Gas (LPG)
Light hydrocarbon material, gaseous at atmospheric temperature and pressure, held in the liquid state by pressure to facilitate storage, transport and handling. Commercial liquefied gas consists essentially of propane, butane, or mixtures thereof.
Liquefied Natural Gas (LNG)
Similar to LPG but consisting of lighter hydrocarbons, such as methane and ethane.
Load Wear Index (LWI)
See four ball test; a measure of the relative ability of a lubricant to prevent wear under applied loads; calculated from the loads applied and corrected for elastic deformation of the balls under static loading and for the size of the wear scar. Formerly called Mean Hertz Load.
A solid to semi-fluid product consisting of dispersion of a thickening agent in a liquid lubricant. Other ingredients for imparting special properties may be included.
A fuel or lubricant additive, usually a chelating agent, which converts into an inactive form, the traces of metal (such as copper in fuels) and metal surfaces (such as copper in fuel lines) which, in the absence of the deactivator, would catalyze gum formation and other oxidation.
U.S. Military Specification
A guide in determining the quality requirements of products used by the military services, published by the United States Department of Defense.
One of the multi-viscosity number oils in which one oil combines three SAE viscosity number grades. For example, multi-grade SAE 10W-40 grade may be used where SAE 10W, SAE 20W-20, SAE 30, or SAE 40 grades are specified. They have been made possible by improved refining processes and the use of polymer additives.
A lubricating grease suitable to meet the individual requirements for chassis lubricant, bearing lubricant, joint lubricant, water-pump lubricant, and cup grease.
One of a group of cyclic hydrocarbons, also termed cycloparaffins or cycloalkanes. Polycyclic members are also found in the higher boiling fractions. The general formula for naphthenes is CnH2n.
The weight, in milligrams, of potassium hydroxide needed to neutralize the acid in 1 g of oil, or the weight, in milligrams, of hydrochloric acid needed to neutralize the base in 1 g of oil. The neutralization number of an oil is an indication of its acidity or alkalinity.
Light overhead cuts of lubricant stocks. Neutral oils are the basis for most commonly used automotive lubricants.
One of a series of numbers classifying the consistency range of lubricating greases, based on the ASTM cone penetration number. The National Lubricating Grease Institute grades are in order of increasing consistency (hardness).
A term numerically indicating the relative antiknock value of a gasoline. For octane numbers 100 or below, it is based upon a comparison with the reference fuels isooctane (100 octane number) and n-heptane (0 octane number). The octane number of an unknown fuel is the percent by volume of isooctane with n-heptane which matches the unknown fuel in knocking tendencies under a specified set of conditions. Above 100, the octane number of a fuel is based on the engine rating, in terms of milliliters of tetraethyllead in isooctane which matches that of the unknown fuel.
One of the shallow grooves cut into the rubbing faces of a bearing shell to improve the distribution of oil over the shaft and bearings. The grooves are connected with an oil supply hole or cup and act like ducts in conveying the oil to the various parts of the bearings.
A loose ring, the inner surface of which rides a shaft or journal causing the ring to rotate. 1. The ring dips into the reservoir of lubricant, from which it carries the lubricant to the top of the shaft for distribution to a bearing. 2. This is the ring on an internal-combustion engine piston which controls the lubrication of the piston and cylinder walls, as contrasted to the compression ring.
1. That characteristic of a liquid which is responsible for the degree of friction between two surfaces which cannot be accounted for on the basis of viscosity alone.
2. The ability of lubricating oil to orient itself on bearing surfaces so as to form new surfaces with a low coefficient of static friction.
3. That characteristic which an oil must possess to a sufficient degree to enable it to overcome every frictional stress to which it is subjected.
A petroleum lubricating or process oil refined until its color, by transmitted light, is straw to pale yellow.
Consistency, expressed as the distance in millimeters that a standard needle or cone penetrates vertically into a sample of the material under known conditions of loading, time, and temperature.
Usually called normal pentane insolubles; the insoluble matter which can be separated from a solution of used lubricating oil in normal pentane and, in addition to the benzene insolubles, may include resinous bitumens produced from the oxidation of oil and fuel. Usually determined in the United States by ASTM Method D-893.
A lubricating oil additive which lowers the pour point of an oil containing wax by reducing the tendency of the wax to form a solid mass in the oil. Also called pour-point depressor, pour depressant.
The lowest temperature at which oil will pour or flow when it is chilled without disturbance under definite conditions. In the United States these conditions are prescribed in ASTM Method D 97.
The ability of a pour-depressant-treated oil to maintain its original ASTM pour point when subjected to storage at low temperature approximating winter conditions.
The number of millimeters of precipitate formed when 10 ml of lubricating oil is mixed with 90 ml of petroleum naphtha of a definite quality and centrifuged under definitely prescribed conditions. The precipitation number should indicate the amount of asphaltic bodies dissolved in the lubricating oil, although a certain amount of paraffin bodies may separate with the asphaltic bodies. A test for precipitation number of lubricating oils is described in ASTM Method D-91.
An oil not used for lubrication but as a component of another material, or as a carrier of other products.
Pumpability (Lubricating Grease)
The ability of a lubricating grease to flow under pressure through the line, nozzle, and fitting of a grease-dispensing system. It is best indicated by the apparent viscosity at moderate rate of shear (see apparent viscosity).
Research Octane Number plus Motor Octane Number, divided by 2. Used now as general measure of road octanes of gasoline.
Rust and oxidation inhibited. Highly-refined industrial lubricating oils formulated for long service in circulating systems, compressors, hydraulic systems, bearing housings, gear cases, etc.
A lubricating oil which, after undergoing a period of service, is collected, reprocessed, and sold for reuse.
Society of Automotive Engineers.
SAE EP Lubricant Tester
A machine designed to test the extreme-pressure properties of a lubricant under a combined rolling and sliding action. The revolving members are two bearing cups which rotate at different speeds.
SAE Viscosity Number
An arbitrary number; one of a system for classifying crankcase oils and automotive transmission and differential lubricants, according to their viscosities, established by the Society of Automotive Engineers. SAE numbers are used in connection with recommendations for crankcase oils to meet various design, service, and temperature requirements affecting viscosity only; they do not connote quality.
A color standard for petroleum products. The procedure for determining Saybolt color and a description of the Saybolt chronometer are given in ASTM Method D-156.
Saybolt Universal Viscosity (SUS or SSU)
The time, in seconds, for 60 ml of fluid to flow through a capillary tube in a Saybolt Universal viscometer at a given temperature, as described in ASTM Method D-88.
A test to determine the tendency of oil to separate from a lubricating grease under conditions prescribed in ASTM Method D-1742.
General term denoting the salt of a fatty acid. The ordinary soaps are those of sodium and potassium. The soaps of lithium, calcium, sodium, and aluminum are the principal thickeners used in grease making.
The ratio of the weight (in air) of a given volume of a material to the weight (in air) of an equal volume of water at stated temperature.
SU (or SUS)
Saybolt Seconds Universal (or Saybolt Universal Seconds).
STLE (formerly ASLE)
Society of Tribologists and Lubrication Engineers. This society has, with the ASTM, established the revised viscosity classification system. Also has published the STLE standards for machine tool lubricants.
Strong Acid Number
The quantity of base, expressed in terms of the equivalent number of milligrams of potassium hydroxide, that is required to titrate the strong acid constituents present in 1 g of sample (ASTM Method D-664 or D-974).
Strong Base Number
The quantity of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide, that is required to titrate the strong base constituents present in 1 g of sample (ASTM Method D-664 or D974).
Defined in ASTM Method D 874 as the ash which remains after a sample of new additive-containing lubricating oil has been carbonized, and the residue subsequently heated with sulfuric acid to constant weight.
A product formed from mineral oil combined with sulfur compounds. It has far greater film strength and load-carrying ability than straight mineral oil and is used as cutting oil.
SUS (or SSU)
Saybolt Universal Seconds (or Saybolt Seconds Universal).
Synthetic Lubricating Oils
Hydrocarbons produced by organic synthesis rather than by extraction or refinement of crud oils.
A descriptive term applied to greases which appear particularly sticky or adhesive.
Tag Closed-Cup Tester
An instrument used to determine the flash point of volatile flammable materials flashing below 175°F, as described in ASTM Method D 56.
Total Acid Number per ASTM Method D 664 or D 974. The milligrams of potassium hydroxide required to neutralize the acid in 1 g of oil.
Total Base Number per ASTM Method D 2896. The milligrams of hydrochloric acid required to neutralize the base in 1 g of oil.
Timken EP test
The Timken Extreme Pressure Test is one of many laboratory machines used in determining the load carrying capacities of oils and greases. In this test, a Timken bearing cup is rotated against a steel block. The highest load under which a lubricant prevents scoring of the steel block by the rotating cup is the reported value.
The measure of the internal friction or the resistance to flow of a liquid. In measuring viscosities of petroleum products, the values of the viscosity in the U.S. are usually expressed as the number of seconds required for a certain volume of the oil to pass through a standard orifice under specified conditions.
Viscosity Conversion Table
A table or chart by means of which kinematic viscosity, in centistokes, can be converted to Saybolt viscosity, in seconds, at the same temperature. Conversion to Saybolt Universal viscosities may be done by the procedures and tables of ASTM Method D 446, and for Saybolt Furol viscosities by ASTM Method D 666. Augmented tables are published in ASTM Special Technical Publication 43B.
Viscosity Index (VI)
Viscosity index is an arbitrary scale used to show the magnitude of viscosity changes in lubricating oils with changes in temperature (ASTM Method D 2270).
The penetration of a sample of lubricating grease immediately after it has been brought to 77°F and then subjected to 60 strokes in a standard grease worker. This procedure and the standard grease worker are described in ASTM Method D 217.