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COMMON 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
coolant’s 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
lubricant’s 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 79ºC/175ºF.
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 lubricant’s 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 engine’s
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 fluid’s 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 engine’s 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 lubricant’s antiwear
qualities, frictional characteristics, or load carrying capabilities. There
are four steel ½-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 engine’s 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 fluid’s resistance to flow under
gravity at a specific temperature (usually 40ºC or 100ºC).
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 0ºC to -40ºC. 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 fuel’s 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 100°F
to an approximate value in cSt at 40°C (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 fluid’s resistance to flow
defined by the ratio of the fluid’s 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 RPM’s.
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 engine’s 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 fluid’s 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 oil’s 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 oil’s 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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