Wear between two surfaces - ploughing,
scratching, polishing by wear debris or solid contaminants.
Acid Number
A measure of the amount of KOH needed
to neutralise all or part of the acidity of a petroleum product.
Additive
Any material added to a base stock
to change its properties, characteristics or performance.
Adhesive Wear
Wear caused by metal-to-metal contact;
welding of asperities in mixed boundary regimes (scoring, scuffing).
Aniline Point
The lowest temperature at which equal
volumes of aniline and hydrocarbon fuel or lubricant base stock are
completely miscible. A measure of the aromatic content of a hydrocarbon
blend, used to predict the solvency of a base stock or the cetane
number of a distillate fuel.
Antifoam Agent
An additive used to change the surface
tension between air and oil so bubbles break rapidly thus preventing
foam formation.
Antiwear Agents
Additives that are activated by rubbing
contact and react to form a protective film over the metal surface
to reduce wear in areas of marginal lubrication.
Apparent Viscosity
A measure of the viscosity of a non-Newtonian
fluid under specified temperature and shear rate conditions.
Ash
Metallic deposits formed in the combustion
chamber and other engine parts during high-temperature operation.
Ash (Sulphated)
The ash content of an oil, determined
by charring the oil, treating the residue with sulphuric acid, and
evaporating to dryness. Expressed as % by mass.
Automatic Transmission Fluid (ATF)
Fluid for automatic, hydraulic transmissions
in motor vehicles.
B
Bactericide
Additive to inhibit bacterial growth
in fluids preventing odours.
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 neutralise acids formed during the
combustion of fuel or oxidation of the lubricant.
Base Number
The amount of acid (perchloric or
hydrochloric) needed to neutralise all or part of a lubricant's basicity,
expressed as KOH equivalents.
Base Stock
The base fluid, usually a refined
petroleum fraction or a selected synthetic material, into which additives
are blended to produce finished lubricants.
Bitumen
Brown/black viscous residue from the
vacuum distillation of crude petroleum. Consists of high molecular
weight hydrocarbons and minor amounts of sulphur and nitrogen compounds.
Also called asphalt and tar.
Black Oils
Lubricants containing asphaltic materials
imparting extra adhesiveness - used for open gears.
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
Partial lubrication between two rubbing
surfaces occurs under high loads as the result of insufficient viscosity,
low speed and restricted contact area.
Bright Stock
A heavy residual lubricant stock with
low pour point, used in finished blends to provide good bearing film
strength, prevent scuffing, and reduce oil consumption. Usually identified
by its viscosity, SUS at 210°F or cSt at 100°C.
Brinelling
Denting caused by impact of one bearing
component against another while stationary.
Brookfield Viscosity
Measure of apparent viscosity of a
non-Newtonian fluid as determined by the Brookfield viscometer at
a controlled temperature and shear rate.
C
Cams
Eccentric shafts used in most internal
combustion engines to open and close valves.
Cam Follower
An engine component that uses a linkage
system between a cam and the valve it operates. The follower typically
translates the rotational motion of the cam to a reciprocating linear
motion in the linkage system.
Carbon Residue
Coked material remaining after an
oil has been exposed to high temperatures under controlled conditions.
Catalytic Converter
An integral part of vehicle emission
control systems since 1975. Oxidising converters remove hydrocarbons
and carbon monoxide (CO) from exhaust gases, while reducing converters
control nitrogen oxide (NOx) emissions. Both use noble
metal (platinum, palladium or rhodium) catalysts that can be "poisoned"
by lead compounds in the fuel or lubricant.
Cavitation Erosion
Wear characterised by formation and
rapid collapse of bubbles on a surface due to rapid pressure changes.
Cetane Index
A value calculated from the physical
properties of a diesel fuel to predict its Cetane Number.
Cetane Number
A measure of the ignition quality
of a diesel fuel, as determined in a standard single cylinder test
engine, which measures ignition delay, compared to primary reference
fuels. 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 Improver
An additive that boosts the Cetane
Number of a fuel.
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.
Cold Cranking Simulator
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.
Compression Ratio
In an internal combustion engine,
the ratio of the volume of combustion space at bottom dead centre
to that at top dead centre.
Corrosion Inhibitor
Additive that protects lubricated
metal surfaces from chemical attack by water or other contaminants.
Corrosive Wear
Wear caused by chemical reaction.
Crown
The top of the piston in an internal
combustion engine above the fire ring, exposed to direct flame impingement.
D
Demulsibility
A measure of a fluid's ability to
separate from water.
Demulsifier
An additive used to prevent the formation
of emulsions by changing the surface tension between oil and water
so separation occurs quickly.
Denaturants
Toxic components used in fuel ethanol
to make it unfit for drinking.
Density
Mass per unit volume.
Detergent Inhibitor
A substance added to a fuel or lubricant
to neutralise acidic blowby gasses, control rust, reduce lacquer and
prevent ring sticking.
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."
Dilution of Engine Oil
Contamination of crankcase oil by
unburned fuel, leading to reduced viscosity and flash point. May indicate
component wear or fuel system maladjustment.
Dispersant
An additive that: helps suspend solid
contaminants in a crankcase oil in colloidal suspension; inhibits
and disperses sludge; reduces the formation of varnish deposits on
engine parts and neutralises combustion acids.
Distillation
The basic test used to characterise
the volatility of a gasoline or distillate fuel.
Dynamic Viscosity
A Measure of the force needed to shear
one fluid layer over another: Shear stress (applied force/unit area) = DV
Shear rate (fluid velocity/gap)
DV =dynamic viscosity
E
Elastohydro-
dynamic Lubrication
A lubricant regime characterised
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 high pressure.
Emulsifier
Additive that promotes the formation
of a stable mixture, or emulsion, of oil and water.
End Point
Highest vapour temperature recorded
during a distillation test of a petroleum stock.
Engine Deposit
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, carbon,
residues from fuel or lubricating oil additives, dust and metal particles
also contribute.
Erosion
Wearing away of a surface by an impinging
solid or fluid.
Exhaust Gas Recirculation
System to reduce automotive emission
of nitrogen oxides (NOx). It routes exhaust gases into the carburettor
or intake manifold where they dilute the air/fuel mixture and reduce
peak combustion temperatures, thereby reducing the tendency for NOx
to form.
F
False Brinelling
Fretting of one bearing component
against another - may appear as a dent but the original surface finish
is worn away.
Fatigue
Cracking, flaking or spalling of a
surface due to stresses beyond the endurance limit of the material.
Ferrography
Magnetic particle analysis.
Flash Point
Minimum temperature at which a fluid
will support instantaneous combustion (a flash) but before it will
burn continuously (fire point). Flash point is an important indicator
of the fire and explosion hazards associated with a petroleum product.
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.
Fretting
Wear resulting from small amplitude
motion between two surfaces - may produce red/black oxide.
Friction
The resistance that one surface encounters
when moving over another.
Frost
Field of micro pits - form of microadhesive
wear.
G
Gaseous Fuels
Liquefied or compressed hydrocarbon
gasses used in motor vehicles in place of gasoline and diesel fuel.
Gasoline
A volatile mixture of liquid hydrocarbons,
containing small amounts of additives and suitable for use as a fuel
in spark-ignition, internal-combustion engines.
Gravity
In petroleum products, the mass/volume
relationship expressed as:
Specigic gravity = mass unit volume product @60F/mass unit volume
water @60F
API gravity = 141.5/specific gravity @60F/60F - 131.5
H
Hydrodynamic Lubrication
Full film lubrication (surface separating).
Hydrodynamic Lubrication
Full film lubrication (surface separating).
Hydrofinishing
Process for treating raw extracted
basestocks with hydrogen for improved stability.
High Temperature
Under engine operating conditions
oils experience high temperature and high shear conditions.
High Shear Viscosity
The viscosity is very different from
that determined using CCS. HTHS is generally measured using a Ravenfield
viscometer which simulates the conditions in a running engine.
I
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 (dust,
wear particles etc).
J
K
Kinematic Viscosity
Measure of a fluid's resistance to
flow under gravity at a specific temperature (usually 40°C or
100°C)
Dynamic Viscosity = Kinematic Viscosity
Density of the fluid
KV 100 relates High temperature operability, oil consumption and SAE
grade.
KV 40 indicates fuel dilution and ISO grade for industrial oils.
KV 40 and KV 100 are used to calculate the viscosity index.
Knock
See Detonation.
L
Lacquer
A thin, insoluble, non-wipeable film
occurring on interior engine parts of diesel engines. Can cause sticking
and damage of moving parts.
Lands
Lands The circumferential areas between
the grooves of a piston.
Lubrication
The support of a sliding load on a
friction-reducing film. The friction reducing film can consist of
gases, liquids or solids.
M
Multigrade 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.
Morphology
The study of the form of things.
N
Naphthenic
Petroleum fluid derived from naphthenic
crude oil - contains a high number of closed-ring hydrocarbons.
Neutralisation Number
A measure of the acidity or alkalinity
of an oil. The number is the mass in milligrams of the amount of acid
(HCl) or base (KOH) required to neutralise one gram of oil.
Neutral Oil
The basis of most commonly used automotive
and diesel lubricants, they are light overhead cuts from vacuum distillation.
Newtonian Flow
An oil is said to show Newtonian behaviour
if shear stress shows a linear relationship to shear rate i.e. viscosity
is independent of shear rate. When rate of shear is not directly proportional
to the shearing force, flow is non-Newtonian, as with oils containing
viscosity modifiers.
Nitration
The process whereby nitrogen oxides
attack petroleum fluids at high temperatures, often resulting in viscosity
increase and deposit formation.
O
P
Paraffinic
A type of petroleum fluid derived
from paraffinic crude oil and containing a high proportion of straight
chain saturated hydrocarbons. Often susceptible to cold flow problems.
Ping
See Detonation.
Pitting
Surface fatigue during rolling contact.
Poise (P)
Measurement unit of a fluid's resistance
to flow, i.e., viscosity, defined by the shear stress (in dynes per
square centimetre) required to move one layer of fluid along another
over a total layer thickness of one centimetre at a velocity of one
centimetre 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.
Pour Point
It is the lowest temperature (°C)at
which the fluid will flow.
Pour Point Depressant
Additive used to lower the pour point
or low-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.
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.
Q
R
Refining
Series of processes to convert crude
oil and its fractions into finished petroleum products, including
thermal cracking, catalytic cracking, polymerisation, alkylation,
reforming, hydrocracking, hydroforming, hydrogenation, hydrogen treating,
solvent extraction, dewaxing, de-oiling, acid treating, clay filtration
and deasphalting.
Rerefining
A process of reclaiming used lubricant
oils and restoring them to a condition similar to that of virgin stocks.
Ridging
In gear teeth, a form of plastic flow
characterised by a rippled appearance on the surface.
Ring Sticking
Freezing of a piston ring in its groove
due to heavy deposits in the piston ring zone.
Rings
Circular metallic elements that ride
in the grooves of a piston and provide compression sealing during
combustion. Also used to spread oil for lubrication.
Rolling and Peening
In gear teeth, a form of plastic flow
that gives the surface a hammered appearance; metal may be rolled
over the teeth tips.
S
Scratching
Fine abrasive furrows in the direction
of sliding.
Scuffing
Abnormal engine wear due to localised
welding and fracture.
Shear Stability Index
A measure of permanent viscosity loss:
SSI = Viscosity loss X 100%
Polymeric viscosity
thickening (lift)
Sludge
A thick, dark residue, normally of
mayonnaise consistency, that accumulates on non-moving engine interior
surfaces. Generally removable by wiping unless baked hard, its formation
is associated with overload of insolubles in the lubricant.
Spalling
Severe damage characterised by large
pits, cavities and cracks; related to overload and fatigue.
Stoke (St)
Kinematic measurement of a fluid's
resistance to flow defined by the ratio of the fluid's dynamic viscosity
to its density.
Synthetic Lubricant
Lubricant made by chemically reacting
materials of a specific chemical composition to produce a compound
with planned and predictable properties.
T
Temporary Shear Stability Index
(TSSI
The measure of the viscosity modifier's
contribution to an oil's percentage viscosity loss under high shear
conditions. Temporary shear loss results from the reversible lowering
of viscosity in high shear areas of the engine, an effect that can
positively influence fuel economy and cold cranking speed.
Temporary Viscosity Loss (TVL)
Measure of decrease in dynamic viscosity
under high shear rates compared to dynamic viscosity under low shear.
Tribology
Science of the interactions between
surfaces moving relative to each other, including the study of lubrication,
friction and wear.
U
V
Valve Lifter
See cam follower.
Varnish
A thin, insoluble, non-wipeable film
occurring on interior engine parts of gasoline engines. Can cause
sticking and malfunction of close-clearance moving parts.
Viscosity
A measure of a fluid's resistance
to flow.
Viscosity Index (VI)
An empirical number indicating the
effect of temperature change on the viscosity of the oil. High VI
means less change of viscosity with temperature.
Viscosity Modifier
Lubricant additive, usually a high
molecular weight polymer, that reduces the tendency of an oil's viscosity
to change with temperature.
