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Automotive Lubrication: Glossary
of Terms
Abrasion - The wearing, grinding, or rubbing away by
friction. Abrasion is usually due to the presence of foreign matter
such as dirt, grit or metallic particles in the lubricant
Absolute Viscosity - The product of Kinematic Viscosity and
Density.
Absolute Viscosity (n) = Kinematic Viscosity (y) x Density (p).
Acid - Corrosive solution formed by the combination of hydrogen
and oxygen atoms with metal or metallic radicals. Acidic solutions may
be neutralized with a base or alkaline solution.
Acid Number - A measure of the amount of KOH needed to
neutralize all or part of the acidity of a lubricant
Additive - Material added to a base stock to change its
properties, characteristics or performance.
Adhesion - The property of a lubricant that causes it to cling
or adhere to a solid surface. Wear occurring when surfaces contact,
weld together and shear off.
Air Entrainment - The incorporation of air in the form of
bubbles dispersed in a fluid. Common when an improper amount of
antifoam agent is added to reduce foaming.
Ambient Temperature - Temperature of the air surrounding the
point of application.
Anhydrous - Free of water.
Antifoam - Additive used to suppress the foaming tendency of
lubricants in service. Improper amounts of antifoam will lead to air
entrainment, which also leads to lubrication problems.
Antifreeze - Solution in an engine cooling system that lowers
the coolants freezing point and raises its boiling point.
Antioxidant (oxidation inhibitor) - An additive that retards
oxidation of lubricants.
Antiwear - Additives that form thin tenacious films on loaded
parts to prevent metal-to-metal contact.
Apparent Viscosity - A measure of the viscosity of a
non-Newtonian fluid under specified temperature & shear. Viscosity is
expressed in units of centipoise (cP).
Ash - Metallic deposits formed in the combustion chamber and
other engine parts during high temperature operation.
Ash (Sulfated) - The ash content of an oil, determined by
charring the oil, treating the residue with sulfuric acid, and
evaporating to dryness. Expressed as % per mass.
Ball Bearing - A class of bearing in which the moving surface
is separated from the stationary surface by elements in the form of
balls.
Bases - Compounds that react with acids to form salts plus
water. Alkalis are water-soluble bases used in petroleum refining to
remove acidic impurities. Oil soluble bases are included in
lubricating oil additives to neutralize acids formed during the
combustion of fuel or oxidation of the lubricant.
Base Stock - The base fluid, usually a refined petroleum
fraction or a selected synthetic material, into which additives are
blended to produce finished lubricants.
Base Number - The amount of acid needed to neutralize all or
part of a lubricants basicity.
Bearing - An object that supports weight and reduces friction
by allowing a surface to rotate or slide when under load.
Biodegradable - Ability of a material can be broken down,
within given parameters of time and environment, by naturally
occurring bacteria into simple substances, which do not harm the
environment.
Bleeding - Separation of liquid lubricant from a grease.
Blow-by - Passage of unburned fuel and combustion gases past
the piston rings of internal combustion engines, resulting in fuel
dilution and contamination of the crankcase oil.
Boundary Lubrication - Lubrication between two rubbing surfaces
without the development of a full fluid lubricating film. It occurs
under high loads and requires the use of antiwear or extreme-pressure
additives to prevent metal-to metal contact.
Brinelling - Denting caused by impact of one bearing component
against another while stationary.
By-Pass Filtration - A system of filtration in which only a
portion of the total flow of a circulating fluid system passes through
a filter at any instant or in which a filter having its own
circulating pump operates in parallel to the main flow.
Carbon Residue - Coked material remaining after an oil has been
subjected to high temperatures.
Cavitation - The formation and collapse of vapor bubbles within
a liquid.
Centipoise (cP) - Unit of measure for apparent viscosity.
Centistoke (cSt) - Unit of measure for Kinematic Viscosity.
Cetane Index - A value calculated from the physical properties
of a diesel fuel to predict its Cetane Number.
Cetane Number - Measure of ignition quality of a diesel fuel.
The higher the Cetane Number, the easier a high-speed, direct
injection engine will start, and the less white smoking and diesel
knock after start up.
Cetane Number Improver - An additive that boosts the Cetane
Number of a fuel while improving combustion efficiency and increasing
power in a diesel engine.
Channel Point - See pour point. As you reduce the temperature
of an oil toward the pour point, you reach a point where you can run
your finger through an oil and it will not fill in the trench you
leave behind. Example: the gearing in the rear end of a car. Although
the gears might move, the gear oil will not flow back into the gear to
lubricate it readily.
Chemical Stability - The tendency of a substance or mixture to
resist chemical change.
Cleveland Open Cup (C.O.C.) - An apparatus used to determine
the flash and fire points of petroleum products other than fuel oils
and those having an open cup flash below 79C/175F.
Cloud Point - The temperature at which a cloud of wax crystals
appears when a lubricant or distillate fuel is cooled under standard
conditions. Indicates the tendency of the material to plug filters or
small orifices under cold weather conditions.
Coefficient of Friction - Number obtained by dividing the
frictional force resisting motion between two bodies (F) by the normal
force pressing the bodies together (L). m = F L
Cohesion - That property of a substance that causes it to
resist being pulled apart by mechanical means.
Cold Cranking Simulator (C.C.S.) - An intermediate shear rate
viscometer that predicts the ability of an oil to permit a
satisfactory cranking speed to be developed in a cold engine.
Combustion Chamber - The space between the piston and cylinder
head in an internal combustion engine where the charge of fuel plus
air is burned to produce power.
Compatibility - A lubricants ability to be mixed with another
lubricant without detriment to either lubricant. Also, the ability to
come into contact with other components or materials without
detrimental effects.
Compound - Substance formed by the combination of two or more
elements with differing physical and chemical properties than the
combining elements.
Compression Ignition - Ignition of fuel by the heat generated
in compressing the air charge, as in the diesel engine.
Compression Ratio - The ratio of the volume of combustion space
at the bottom dead center to that at top dead center, in an internal
combustion engine.
Consistency - The degree to which a semi-solid material such as
grease resists deformation.
Contaminant - Any material that is unwanted or adversely
affects the fluid power system and/or its components.
Coolant - Fluid used to remove heat. Commonly found in an
engines cooling system.
Copper Strip Corrosion - Qualitative measure of the tendency of
a liquid to corrode pure copper.
Corrosion - Destruction of a metal by chemical or electo-chemical
reaction with its environment.
Corrosion Inhibitor - Additive that protects lubricated metal
surfaces from chemical attack by water or other contaminates.
Cracking - Refining process in which large molecules are broken
down into smaller molecules. Cracking takes place to some extent
whenever high molecular material is heated strongly, but can be
increased by catalysts.
Crankcase - The housing in which the crankshaft and many other
parts of the engine operate. On a two-cycle engine, the area in which
the fuel/oil mixture is drawn before being transferred to the
cylinder.
Crankcase Dilution - When unburned fuel finds its way past the
piston rings into the crankcase oil, where it dilutes or thins out the
engine lubricating oil.
Crude Oil - Naturally occurring petroleum, before any refining
or treatment.
Demulsibility - The measure of a fluids ability to separate
from water.
Density - Mass per unit of volume.
Detergent - Additive to keep engine parts clean. In motor oil
formulations, the most commonly used detergents are metallic soaps
with a reserve of basicity to neutralize acids formed during
combustion.
Detonation - Uncontrolled burning of the last portion (end gas)
of the air/fuel mixture in the cylinder of a spark-ignition engine.
Also known as knock or ping.
Differential - Set of gears that transfers the power from the
drive shaft to the drive wheels and allows those wheels to turn at
different speeds.
Dispersant - Additive that helps keep solid contaminants in
crankcase oil in colloidal suspension, preventing sludge and varnish
deposits on engine parts. Usually nonmetallic (ashless), and used in
conjunction with detergents.
Distillation - Separation of a mixture of liquids with
different boiling points by progressively raising the temperature. In
a refinery distillation unit the temperature rises continuously from
the top to the bottom of the column and different fractions or cuts
are drawn off at different heights.
Distillation Test - The basic test used to characterize the
volatility of a gasoline or distillate fuel.
Drag - Resistance to movement caused by oil viscosity.
Dropping Point - Temperature at which a grease passes from a
semi-solid to a liquid state under specified test conditions.
Drum - A cylindrical container that holds 55 gallons of oil or
approximately 400 pounds of grease type products. There are also
half-size drums that hold approximately 30 gallons of oil.
Dynamic Viscosity - Viscosity of a liquid as measured in a
rotational instrument, as distinct from the kinematic viscosity where
the liquid falls through a capillary tube under its own weight.
E.G.R. (Exhaust Gas Recirculation) Valve - System to reduce
automotive emission of nitrogen oxides (Nox). It routes exhaust gases
into the intake manifold where they dilute the air/fuel mixture and
reduce peak combustion temperatures, thereby reducing the tendency for
Nox to form.
Elastohydrodynamic Lubrication (EHD or EHL) - Lubrication
characterized by high unit loads and high speeds in rolling elements
where the mating parts deform elastically due to the incompressibility
of the lubricant film under very high pressure.
Elastomer - A rubbery type of material.
Emissions - Term used generically to refer to the various
components of the engines exhaust.
Emulsifier - Substance used to promote or aid the formation of
a stable mixture, or emulsion of oil & water.
Emulsion - Mixture of two liquids, which are not soluble with
each other, such as oil and water.
Engine Deposits - Hard or persistent accumulation of sludge,
varnish and carbonaceous residues due to blow-by of unburned and
partially burned fuel, or the partial breakdown of the crankcase
lubricant. Water from the condensation of combustion products, glycol,
carbon, residues from fuel or lubricating oil additives, dust and
metal particles also contribute.
EP (Extreme Pressure) - Lubrication regime where surfaces are
sliding against each other under heavy load. The expression was coined
for the condition present in hypoid gears in automotive rear axles.
EP (Extreme Pressure) Lubricants - Lubricants that impart to
rubbing surfaces the ability of carrying greater loads than would be
possible with ordinary lubricants without excessive wear or damage.
Erosion - The wearing away of a surface by an impinging fluid
or solid
Ester - An organic compound formed by the reaction of an acid
(organic or inorganic) with an alcohol.
Ethanol - Ethyl alcohol mainly formed through fermentation.
(alcoholic drinks, component in gasohol)
Ethylene Glycol - A colorless, syrupy liquid, used as an
antifreeze in cooling and heating systems.
Evaporation Loss - The loss of a portion of a lubricant due to
volatization.
Fillers - A term normally used to denote something non-chemical
added to an oil or grease, i.e., moly, graphite, zinc oxide.
Film Strength - The ability of a lubricant film to withstand
the effects of speed, temperature and load without breaking down.
Filter - Any device or porous substance used for cleaning and
removing suspended matter from a gas or fluid.
Fire Point - The temperature where a lubricant, when subjected
to a source of ignition or flame, ignites & continues to burn.
Fire Resistant Fluid - A fluid, difficult to ignite, that shows
little tendency to propagate flame.
Flash Point (C.O.C.) - The temperature to which a combustible
liquid must be heated to give off substantial vapor to form a
momentarily flammable mixture with air when a small flame is applied
under specific conditions.
Fluid - Liquid, gas or combination thereof.
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.
Fluid Power - Energy transmitted and controlled through use of
a pressurized fluid within an enclosed circuit.
Foam - An agglomeration of gas bubbles separated from each
other by a thin liquid film. If an oil is said to not foam, the small
air bubbles will quickly combine, become larger bubbles, and then
break to vent to the atmosphere. If this action occurs slowly, the oil
is said to foam.
Four Ball Test - Machine used to evaluate a lubricants antiwear
qualities, frictional characteristics, or load carrying capabilities.
There are four steel -inch balls. Three of the balls are clamped
together in a cup filled with lubricant while the fourth ball is
rotated against them. Two test procedures are based on this same
principle the Four Ball EP Test (ASTM D-2596) and Four Ball Wear Test
(ASTM D-2266).
Four Stroke Engine - An internal combustion engine that
requires two revolutions of the crankshaft to complete all four
cycles.
Fretting - Wear resulting from small amplitude motion between
two surfaces; may produce red or black oxide.
Friction - Resistance to motion of one object over another.
Friction depends on the smoothness of the contacting surfaces, as well
as the force with which they are pressed together.
Fuel Dilution - The amount of unburned fuel present in the
lubricant. This test will indicate problems such as fuel line,
injector, carburetor and pump leaks. Fuel dilution is accurate down to
less than 0.5%.
Full Film Lubrication - Complete separation of mated surfaces.
No metal-to-metal contact.
Full-Flow Filtration - A system of filtration in which the
total flow of a circulating fluid system passes through a filter prior
to component delivery.
Gears - Toothed machine parts for transmitting power from one
shaft to another.
Gravity - The mass/volume relationship of lubricants used in
determining volume requirements for specific mass of products
(packaging).
Grease - Lubricant composed of an oil or oils thickened with a
soap, soaps or other thickener to a semi-solid consistency.
Gum - A rubber like, sticky deposit black or dark brown in
color resulting from the oxidation of lubricating oils from unstable
constituents in gasoline, which deposit during storage or use.
High Temperature High Shear Rate Viscosity (HTHS) - A measure
of a fluids resistance to flow under conditions resembling
highly-loaded journal bearings in fired internal combustion engines,
typically 1 million s-1 at 150oC.
Horsepower - A measurement of an engines power, equal to 550
foot pounds of torque per second.
Hydrocarbons - Compounds of hydrogen & carbon of which
petroleum products are typical examples. Also known as organic
compounds.
Hydrodynamic Lubrication - The formation of a continuous
lubricating fluid film between mating surfaces of sufficient pressure
to prevent contact
Hydro finishing - A process for treating raw extracted base
stocks with hydrogen to saturate them for improved stability.
Hydrolytic Stability - Ability of additives and certain
synthetic lubricants to resist chemical decomposition (hydrolysis) in
the presence of water.
Hypoid Gear Lubricant - A gear lubricant having extreme
pressure characteristics for use in hypoid type gears (as in the
differential of an automobile).
Incompatibility - When a mixture of two or more substances
shows physical properties or service performance characteristics,
which are inherently inferior to those of either of the individual
products before mixing.
Inhibitor - Additive that improves the performance of a
petroleum product by controlling undesirable chemical reactions, i.e.,
oxidation inhibitor, rust inhibitor, etc.
Insolubles - Contaminates found in used oils due to dust, dirt,
wear particles or oxidation products.
Journal - Part of shaft or axle that rotates or angularly
oscillates in or against a bearing or about which a bearing rotates or
angularly oscillates.
Keg - Container which would typically hold 16 gallons of oil or
approximately 120 pounds of a grease-type product. Also called a
quarter drum.
Kinematic Viscosity - Measure of a fluids resistance to flow
under gravity at a specific temperature (usually 40C or 100C).
Lubrication - Control of friction and wear by the introduction
of a friction reducing film between moving surfaces in contact. May be
a fluid, solid or plastic substance.
Material Safety Data Sheet (MSDS) - Vital information regarding
the safe handling and storage of a product.
Micron - A millionth of a meter, or 0.0000394 inch.
Mineral Oil - Term applied to a wide range of products that is
typically used when referring to petroleum-based lubricants.
Mini Rotary Viscometer - An instrument used to measure the
borderline pumping temperature (BPT) of engine oils from 0C to -40C.
BPT is the lowest temperature at which engine oil can be supplied in
adequate amounts to the oil pump inlet.
Multi-viscosity/Multi Grade Oil - Engine or gear oil that meets
the requirements of more than one SAE viscosity grade classification,
and that can be used over a wider temperature range than a single
grade oil.
Naphthenic - A type of petroleum fluid derived from naphthenic
crude oil, containing a high proportion of closed-ring methylene
groups.
Neutralization Number - A measure of the acidity or alkalinity
of an oil.
Newtonian Flow - Occurs in a liquid system where the rate of
shear is directly proportional to the shearing force, as with straight
grade oils which do not contain polymeric viscosity modifier. When
rate of shear is not directly proportional to the shearing force, flow
is non-Newtonian, as it is with oils containing viscosity modifiers.
Nitration - Process where nitrogen oxides attack petroleum
fluids at high temperatures, often resulting in viscosity increase and
deposit formation. Nitration only occurs in applications where fuel is
used.
NLGI - National Lubricating Grease Institute, an industry group
that monitors grease and sets penetration standards for grading
greases.
NLGI Number - A scale for comparing the consistency (hardness)
range of greases.
Octane Number - A measure of a fuels ability to prevent
detonation in a spark-ignition engine.
Organic Acid - An organic compound, with acid properties,
obtained from organic substances such as animal, vegetable and mineral
oils, i.e., a fatty acid.
Oxidation - Occurs when oxygen attacks fluids. The process is
accelerated by heat, light, metal catalysts and the presence of water,
acids, or solid contaminants. It leads to increased viscosity and
deposit formation.
Oxidation Inhibitor - Substance added in small quantities to an
oil product to increase its oxidation resistance, thereby lengthening
its service or storage life. Also called an antioxidant.
Oxidation Stability - Resistance of an oil product to oxidation
and, therefore, a measure of its potential service or storage life.
Oxygenated Fuels - Fuels for internal combustion engines that
contain oxygen combined in the molecule, e.g., alcohols, ethers and
esters. Term also applies to blends of gasoline with oxygenates, e.g.,
Gasohol, which contains 10% by volume of anhydrous ethanol in unleaded
gasoline.
Paraffin - Hydrocarbons belonging to the series starting with
methane (CH4). Paraffins are saturated with respect to hydrogen. High
molecular weight paraffins are solid such as paraffin wax.
Particle - A minute piece of matter with observable length,
width and thickness, usually measured in micrometers.
PCV (Positive Crankcase Ventilation) Valve - An emissions
control device that allows gases from the crankcase to be reintroduced
into the intake.
Penetration - A test in which a cone is dropped into a grease
sample to measure the penetration or how hard or soft the grease is at
room temperatures. The cone penetrates farther in a soft grease and
therefore has a higher penetration number. This penetration relates to
an NLGI number. A number 0 grease is called an NLGI 0 grade and will
be softer than an NLGI 1 or 2 grade.
pH - A measure of acidity or alkalinity. Values of pH run from
0-14; 7 indicating neutrality, numbers less than 7 indicate increasing
acidity, and numbers greater than 7 indicate increasing alkalinity.
Pitting - Surface cavities, may be related to fatigue, overload
or corrosion.
Pneumatics - Engineering science pertaining to gaseous pressure
and flow.
Poise - Unit of viscosity, defined by the shear stress required
to move one layer of fluid along another over a total thickness of one
centimeter at a velocity of one centimeter per second. This viscosity
is independent of fluid density, and directly related to flow
resistance.
Polishing (bore) - Excessive smoothing of the surface finish of
the cylinder bore or cylinder liner in an engine to a mirror-like
appearance, resulting in depreciation of ring sealing and oil
consumption performance.
Polymerization - Chemical combination of similar type molecules
to form larger molecules.
Pour Point - An indicator of the ability of an oil or
distillate fuel to flow at cool operating temperatures. It is the
lowest temperature at which the fluid will flow when cooled under
prescribed conditions.
Pour Point Depressant - Additive used to lower the pour point
or lower the temperature fluidity of a petroleum product.
Preignition - Ignition of the fuel/air mixture in a gasoline
engine before the spark plug fires. Often caused by incandescent fuel
or lubricant deposits in the combustion chamber, it wastes power and
may damage the engine.
Propylene Glycol - A non-toxic liquid used as a
coolant/antifreeze in cooling and heating systems.
Pumpability - The low temperature, low shear stress-shear rate
viscosity characteristics of an oil that permit satisfactory flow to
and from the engine oil pump and subsequent lubrication of moving
components.
Refining - Series of processes to convert crude oil and its
fractions into finished petroleum products, which may include thermal
cracking, catalytic cracking, polymerization, alkylation, reforming,
hydrocracking, hydrofoaming, hydrogenation, hydrogen treating,
Hydrofining, solvent extraction, dewaxing, de-oiling, acid treating,
clay filtration, deasphalting, etc.
Re-refining - A process of reclaiming used lubricant oils and
restoring them to a condition similar to that of virgin stocks by
filtration, clay adsorption or more elaborate methods.
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.
Rust - Slow oxidation of iron.
Rust Preventative - Compound for coating iron surfaces with a
film that protects against rust. Commonly used to preserve equipment
in storage.
SAE Grade - Numbers applied to automotive lubricants to
indicate their viscosity range.
Saybolt, Saybolt Universal Seconds, SUS, or SSU - The most
common viscosity measurement prior to the international acceptance of
centistokes, SUS measurements are now obsolete. To convert
measurements from SUS at 100F to an approximate value in cSt at 40C
(ISO viscosity grade), divide the SUS value by 5.
Scoring - Scratches on mechanical parts in the direction of
motion caused by abrasive contaminants.
Scuffing - Abnormal engine wear due to localized welding and
fracture. It can be prevented through the use of antiwear,
extreme-pressure and friction modifier additives. See adhesion.
Semi Fluid - Any substance having attributes of both a liquid
and a solid. Similar to semi solid but being more closely related to a
liquid than a solid.
Shearing - Relative slipping or sliding between one part of a
substance and an adjacent part.
Shear Stability - Ability of a lubricant to withstand shearing
forces without being degraded to lower viscosity or consistency.
Sludge - A thick, dark residue, normally of mayonnaise
consistency, that accumulates on nonmoving engine interior surfaces.
Generally removable by wiping unless baked into a carbonaceous
consistency, its formation is associated with insolubles overloading
the lubricant.
Solid - Any substance having definite shape that it does not
readily relinquish. More generally, any substance in which the force
required to produce a deformation depends upon the magnitude of the
deformation rather than the rate of deformation.
Stoichiometric - Ratio of fuel to air where the exact
proportions for complete reaction of both, with none left over, are
present.
Stoke (St) - Kinematic measurement of a fluids resistance to
flow defined by the ratio of the fluids dynamic viscosity to density.
Supercharger - A device for increasing the pressure and hence
the mass of air and fuel burned on each firing stroke. Driven by the
crankshaft; therefore, displacement is fixed and directly related to
engine RPMs.
Surface Tension - The contractile surface force of a liquid by
which it tends to assume a spherical form and to present the least
possible surface. It is expressed in dyne/cm or ergs/cm.
Synthetic Lubricant - Fluid made by chemically reacting
materials to produce a lube with a specific chemical composition,
which has planned, and predictable properties.
Thermally Stable - Ability to withstand temperatures without
decomposing. Not to be confused with oxidation stability where oxygen
must be present and oxidation rather than decomposition.
Thickener - The metallic soap or other material used to combine
with oil or other lubricating fluid to make a grease.
Torque - The twisting force with which the engines crankshaft
actually rotates, measured in foot-pounds.
Total Acid Number (TAN) - The quantity of base, expressed in
milligrams, that is required to neutralize all acidic constituents
present in one gram of sample.
Total Base Number (TBN) - The quantity of acid, expressed in
terms of the number of milligrams that is required to neutralize all
basic constituents present in one-gram sample.
Total Solids - The total amount of solids contamination, both
suspended and non-suspended present in the lubricant. This test is
indicative of carburetion problems (too rich or too lean), if the oil
filter has reached the saturation point and is no longer able to
remove contamination from the system, and if the air intake system is
functioning properly and allowing enough air into the unit for
complete burn to take place.
Tribology - Science of the interactions between surfaces moving
relative to each other, including the study of lubrication, friction
and wear.
Turbine - A device consisting of blades attached to a disc or
rotor, which converts flow into rotary action.
Turbocharger - A device for increasing the pressure and hence
the mass of air and fuel burned on each firing stroke. A turbine of
exhaust gases drives a compressor; therefore, efficiency is variable
and related to exhaust pressure.
Vapor Lock - Condition wherein the fuel boils in the fuel
system forming bubbles that retard or stop the flow of fuel to the
engine.
Varnish - A thin, insoluble, non-wipeable film occurring on
interior engine parts.
Viscosity - Measure of a fluids resistance to flow.
Viscosity Index (V.I.) - Relationship of viscosity to
temperature of a fluid. High viscosity index fluids tend to display
less change in viscosity with temperature than low viscosity index
fluids.
Viscosity Index Improver (V.I.I.) - Additive to improve or
increase the viscosity index. A VI improver increases an oils
resistance to thinning as it is heated. It is commonly used in
multi-viscosity or multigrade oils. Since a VI improver increases the
viscosity as well as the viscosity index, it must be taken into
consideration when formulating oil. (Example: taking an oil in the SAE
30 range, adding a VI improver could give an oil like a SAE 40)
Viscosity Modifier - See V.I.I. Additive, usually a high
molecular weight polymer that reduces the tendency of an oils
viscosity to change with temperature.
Wear - Damage resulting from the removal of materials from
surfaces in relative motion.
Zinc (ZDP) - Commonly used name for zinc dithiophosphate, an
antiwear/oxidation inhibitor chemical.
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