ACEA - Association of European Automotive
AGMA - American Gear Manufacturers Association
API - American Petroleum Institute
ASLE - American Society of Lubrication Engineers
ASME - American Society of Mechanical Engineers
ASTM - American Society for Testing and
BPT - Borderline Pumping Temperature
BTU - British Thermal Unit
CARB - California Air Resources Board
CCS - Cold Crank Simulator
CEC - Conseil Europen de Coordination pour
CMA - Chemical Manufacturers Association
cP - CentiPoise
cSt - CentiStoke
COC - Cleveland Open Cup
DIN - Deutsche Industrie Norm
EGR - Exhaust Gas Recirculation
EHD or EHL - Elastohydrodynamic
EMA - Engine Manufacturers Association
EP - Extreme Pressure
ILSAC - International Lubricant Standardization
and Approval Committee
ISO - International Organization for Standardization
JAMA - Japanese Automobile Manufacturers
JASO - Japan Automobile Standards Organization
SDS - Safety Data Sheet
NLGI - National Lubricating Grease Institute
NMMA - National Marine Manufacturers Association
PAO - Polyalphaolefin
SAE - Society of Automotive Engineers
STLE - Society of Tribologists and Lubrication
SUS or SSU - Saybolt Universal
TAN - Total Acid Number
TBN - Total Base Number
VI - Viscosity Index
VII - Viscosity Index Improve
ZDDP - Zinc Dialkyl Dithiophosphate
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
Additive - Material added to a base oil
to change its properties, characteristics or performance.
Adhesion - The property of a lubricant that
causes it to cling or adhere to a solid surface.
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 percent
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 Oil - 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 to
be broken down, within given parameters of time and environment,
by naturally occurring bacteria into simple substances that
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
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.
Bypass 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
Centistoke (cSt) - Unit of measure for Kinematic
Cetane Index - A value calculated from the
physical properties of a diesel fuel to predict its Cetane
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 startup.
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 79°C/175°F.
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
Coefficient of Friction - Number obtained
by dividing the frictional force resisting motion between
two bodies (F) by the normal force pressing the bodies together
Cohesion - That property of a substance
that causes it to resist being pulled apart by mechanical
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
a 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 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
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-stroke
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
Distillation Test - The basic test used
to characterize the volatility of a gasoline or distillate
Drag - Resistance to movement caused by
Dropping Point - Temperature at which a
grease passes from a semi-solid to a liquid state under specified
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
Emulsion - Mixture of two liquids that
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
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
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 volatilization.
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
Fire Point - The temperature at which a lubricant,
when subjected to a source of ignition or flame, ignites
& continues to burn.
Fire-Resistant Fluid - A fluid
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
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
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 D2596) and Four-Ball Wear Test (ASTM
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 and the force with which they are pressed
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 percent.
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
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 fluid's resistance to flow under conditions
resembling highly loaded journal bearings in fired internal
combustion engines, typically 1 million s-1 at 150C°.
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 oils 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).
When a mixture of two or more substances shows physical properties
or service performance characteristics inherently
inferior to those of either of the individual products before
Inhibitor - Additive that improves the performance
of a petroleum product by controlling undesirable chemical
reactions, i.e., oxidation inhibitor, rust inhibitor, etc.
Insolubles - Contaminants 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
Keg - Container that
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 40°C or 100°C).
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.
Safety Data Sheet (SDS)
- Vital information regarding the safe handling and storage
of a product.
Micron - A millionth of a meter, or 0.0000394
Mineral Oil - Term applied to a wide range
of products that is typically used when referring to petroleum-based
Mini Rotary Viscometer - An instrument used
to measure the borderline pumping temperature (BPT) of engine
oils from 0°C to -40°C. BPT is the lowest temperature at which
engine oil can be supplied in adequate amounts to the oil
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
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
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 temperature. 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 with 7 indicating neutrality. Numbers
less than 7 indicate increasing acidity, and numbers greater
than 7 indicate increasing alkalinity.
Pitting - Surface cavities that 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
1 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
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.
Semi-Fluid - Any substance having attributes
of both a liquid and a solid. Similar to semi-solid but
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.
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 with 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
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 a 1-gram 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 a 1-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
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
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
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 - 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 (ZDD) - Commonly
used name for zinc dialkyl dithiophosphate, an antiwear/oxidation