Glossary

Abrasive wear - Wear between two surfaces caused by the relative motion of two surfaces or three when particles are between the sliding surfaces.

Abrasive wear - When there is metal to metal contact between sliding surfaces, the microstructure welds causing damage to the surfaces. Adhesive wear results.

Absolute viscosity - absolute viscosity = kinematic viscosity x density

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Acid number - Amount of potassium hydroxide (KOH) required to neutralise the acidic components in a sample of petroleum products.

Additive - Any material that is added in low concentration to a bulk liquid (for lubricants or liquid fuels) to improve the performance of the base fluid or give it new properties.

Air release - The time it takes for entrained air within a sample of oil product to escape.

Aniline point - The lowest temperature at which equal volumes of aniline and hydrocarbon fuels or lubricant are completely miscible. Strange as it seems, temperature affects how liquids mix. Aniline point is used to measure the aromatic content of a hydrocarbon blend. Thus, the solvency characteristics of a lubricants base stock or the cetane number of distillate fuel can be determined.

Anti-foam agent - An additive used to suppress the foaming in petroleum products. If too much is added, can promote foaming and cause corrosion.

Anti-oxidant - An additive, which inhibits the oxidation of oils.

Anti-static agent - Additives, which increase the conductivity of petroleum products, thereby dissipate electrostatic charges and reduce the explosion and fire hazard.

Anti-wear agent - Additive, which binds with the surface of components and prevents wear by forming a barrier between sliding surfaces. Termed physisorbed if they weakly bind with the surface and chemisorbed when they react with the surface.

API gravity - 141.5 divided by specific gravity @60 deg C then minus 131.5

Apparent viscosity - A measure of the viscosity of a non-Newtonian fluid under specified temperature and shear conditions. Typically used to describe greases.

Aromatic - Petroleum product containing benzene ring type molecules. Benzene is a six carbon ring molecule.

Ash - Metallic deposit 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 and treating the residue with sulphuric acid and evaporating to dryness. Expressed as % of original mass.

Automatic Transmission Fluid (ATF) - Fluid for the automatic transmissions in motor vehicles.

Bacteriocide - Additive to inhibit or kill bacterial growth. Typically used in aqueous fluids such as water-based cutting fluids. All bactericides have an optimum concentration for usage, too little is ineffective, too much and they can attack the skin and cause irritation.

Base number - The amount of acid (perchloric or hydrochloric) needed to neutralise all or part of the lubricant's basicity, expressed as potassium hydroxide equivalents.

Base oil credit - In lubricating cost calculations, the value of the base fluid displaced by the additive package.

Base stock - The base fluid, usually a refined petroleum component or synthetic oil (made by chemical reaction), into which additives are blended to produce finished lubricants.

Bases - Compounds which react with acids to form salts plus water. Alkalis are water-soluble bases. Oil soluble bases are used in lubricating oil formulations to neutralise acids formed during combustion of fuels or the acids produced during the oxidation process. In marine oil formulations, the base content can be quite high to neutralise the acids produced when burning high sulphur content fuels.

Bitumen - Is the brown/black viscous residue from the vacuum distillation of crude oil. Composed of high molecular weight hydrocarbons, with minor amounts of sulphur and/or nitrogen containing molecules. Sometimes referred to as asphalt or tar.

Black oils - Lubricants containing asphalt materials. These impart adhesive properties to the lubricant and are often used in open gear applications.

Bleeding - The tendency of a liquid component to separate from a solid or semi-solid mixture. Commonly seen when oil separates from grease.

Blow-by - Passage of unburnt fuel and combustion gases past the piston rings of engines. Results in so-called fuel dilution of the crankcase lubricant.

Boundary lubrication - Limited separation of two moving surfaces when the liquid film breaks down. For example under high loads, low speed or limited contact area. To prevent welding and resulting adhesive wear, anti-wear or extreme-pressure additives are added.

Bright stock - Refined high viscosity lubricating oils, used in lubricants to maintain a stable film between surfaces.

Brinelling - Denting caused by impact of one bearing component against another whilst stationary.

Brookfield viscosity - Measure of the apparent viscosity of non-Newtonian fluids as determined by a Brookfield viscometer at a controlled temperature and shear rate.

Carbon residue - Measure of the amount of carbonous material left behind after exposing the lubricant or oil to high temperatures under controlled conditions.

Cavitation erosion - Wear characterised by the formation and rapid collapse of bubbles on the component surface.

Centipoise (cP) - Unit of absolute viscosity.

Centistoke (cSt) - A standard unit of kinematic viscosity.

Cetane index - A value calculated from the density and distillation mid-point temperature of a fuel, used as an alternative to cetane number to indicate relative diesel ignition quality.

Cetane number - A measure of the ignition quality of diesel fuel, as determined by a standard single cylinder engine test. The higher the number, the easier a high speed diesel engine will be to start, less white smoke and diesel knock after start-up.

Cetane number improver - Additive, which improves the cetane number of diesel fuels.

Channel point - Lowest safe temperature that a gear lubricant can be used.

Cleveland open cup (COC) - Method to determine the flash and fire points of petroleum based products.

Cloud point - Temperature at which a noticeable cloud of wax crystals appears when a sample of petroleum-based product is cooled under standard conditions. These wax crystals can block filters or other narrow pipes or pores. Hence cloud point important when determining the acceptability of diesel fuels for winter usage.

Coefficient of friction - The ratio of the friction force between two bodies to the normal or perpendicular force between them.

Cold cranking simulator (CCS) - An intermediate shear rate viscometer that predicts the ability of an oil to permit satisfactory cranking speed in a cold engine.

Compounded oil - Commonly used industry term to describe a lubricant containing fats to impart lubricity eg cutting oils for aluminium, steam cylinder oils.

Compression oil - The ratio of combustion space at bottom dead centre to that at top dead centre in an internal combustion engine.

Copper strip corrosion - A measure of the corrosivity of lubricants on copper.

Corrosion inhibitor - Additives that protect metal surfaces from chemical attack by water or other contaminant.

Cutting oil or fluid - Lubricants used in the process of cutting metals or other materials. These generally cool and lubricate the tools tips, thus extending tool life and promoting smoother component finish.

Defoamant (foam inhibitor) - Additive used in lubricating oils to assist the collapse of surface layers of foam.

Demulsibility - A measure of a fluids ability to separate from water. The higher the demulsibility the faster the fluid separates from water.

Denaturant - Noxious or toxic components added to usually alcohols to make them unfit for human consumption.

Density - mass per unit volume ie mass/volume

Detergency - Ability of a lubricating oil to reduce or prevent deposits formed under high temperature conditions or as a result of acidic components formed during combustion.

Detergent - An additive added to formulations to keep surfaces clean. In engine oil formulations, these are commonly metallic soaps with some basicity to both combine with and neutralise acids and carboneous materials formed during combustion.

Detonation - Uncontrolled burning of the last portion of the air/fuel mixture in the cylinder of a spark ignition engine. Also known as "knock."

Dewaxing - The process which removes wax from the lubricant distillate in the refining process by solvent or catalytic means.

Dielectric strength - Measure of the insulating value of an electrical insulating medium. Important for electro discharging machining (EDM) and transformer oils.

Disperancy - Ability of an oil to disperse and suspend fine particles which could form deposits, in solution.

Distillate - A component of distillation eg kerosine, lubricant base stocks etc.

Distillation - Term used to describe the process of heating up a liquid to separate the different boiling fractions. Used in crude oil refining to produce fuel and lubricant base stocks.

Dropping point - Temperature at which the first drop of liquid separates when a grease is heated under prescribed conditions. For example, the temperature at which grease converts from a semi-solid to a liquid.

Dynamic viscosity - see absolute viscosity.

Elastohydrodynamic lubrication - The lubricant regime characterised by high unit loads and high speeds in rolling elements where elastic deformation of the mating parts occurs due to the incompressibility of the lubricant film under high pressure.

Emission control systems - Equipment designed to reduce the level of atmospheric pollutants released to the atmosphere.

Emulsifier - An additive that promotes the formation of emulsions. For example, oil and water separate when mixed, with the addition of the correct emulsifiers, the mixture when shaken becomes a stable solution.

Emulsion - Intimate mixture of two or more liquid components which are incompatible or partially miscible with each other. So-called "soluble" oil cutting fluids typically contain over 60% oil in the concentrate and form a white emulsion when mixed with water. Micro-emulsion cutting fluids form sub-micron droplets when mixed with water and are thus translucent or transparent in nature.

End point - Highest vapour temperature recorded during a distillation test of a petroleum stock.

Engine deposits - Hard or persistent accumulation of sludge, varnish and carbonaceous residue due to blow-by of unburnt and partially burnt 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.

Exhaust gas recirculation (ERG) - System to reduce automotive emissions of nitrogen oxides (NOx). It routes exhaust gases into the combustion chamber via the inlet manifold or carburettor, where they dilute the air/fuel mixture and reduce peak combustion hereby reducing NOx formation.

Extreme Pressure (EP) additives - Prevent the sliding metal surfaces from seizing under extreme pressure conditions. Commonly used in cutting oil formulations to extend tool life.

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 spiralling of a surface due to stresses beyond the endurance limit of the material.

Fatty acid - Straight chain organic acid.

Ferrography - Magnetic particle analysis. From a detailed study of the particles in an oil, it is possible to predict failure and take preventive maintenance.

Filler - Any solid substance such as talc and other powders which is normally added to grease to increase weight, consistency etc.

Filter - A device to clean oils of particulate matter.

Fire point (Cleveland open cup) - The flash point of an oil is the temperature to which it must be heated to give off sufficient vapour to form momentarily, a flammable mixture with air when a small flame is applied under specified conditions.

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 petroleum products.

Floc point - The temperature at which a flocculent collection of wax crystals first appears when a solution of freon in an oil is cooled under prescribed conditions. Also used to describe the temperature at which a flocculant forms when heating a poly alkylene glycol solution in water.

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.

Force feed lubrication - Usually automatic lubrication systems supply the lubricant under pressure to the bearings.

Forming oil - A lubricant usually sprayed onto wood or metal moulds, into which concrete is poured. The lubricant ensures that the concrete does not stick to the moulds and determines surface finish. Also used to describe lubricants used in metal forming operations.

Fretting corrosion - A process of mechanical attrition combined with chemical reaction. Usually takes place at the boundary of loaded contact surfaces moving in oscillatory motion.

Friction - Resistance to motion of one object over another. Friction depends one surface texture, as well as the forces acting on the components.

Frost - Field of micro pits and a form of adhesive wear.

Full flow filtration - A system of filtration in which the total flow of circulating oil passes through the filter.

FZG load stage - The load which can be transmitted by a pair of gears under the conditions of test and temperature in the FZG machine before failure of the gear surface occurs. Normal running temperature 90 deg C.

Galling - see adhesive wear

Gaseous fuels - Hydrocarbon gases (methane, ethane, propane, butane) which are used as internal combustion engine fuels.

Gasohol - A blend of gasoline and methanol or ethanol for use in spark ignition engines.

Graphite - A platelet form of carbon, which is used in lubricants to impart lubricity under high loads.

Gravity - In petroleum products, the mass/volume relationship expressed as:
mass/unit volume product @ 60 deg F
Specific gravity = -----------------------------------------------
mass/unit volume water @ 60 deg F

Grease - A lubricant composed of an oil or oils thickened with a soap or other thickener to make a solid or semi-solid product.

Gum - A rubber like, sticky deposit, black or brown in colour which is the by-product of the oxidation of some lubricating oils in service.

Hydraulic oils - a lubricant specially formulated for use as a power transmission medium in hydraulic equipment.

Hydro-finishing - process for treating raw extracted base stocks with hydrogen to improve stability.

Hydro-treating - a process which converts and removes undesirable components with the use of a catalyst.

Hydrodynamic lubrication - full film lubrication ie the fluid is totally separating the moving surfaces.

Hydrolytic stability - the ability of additives and certain synthetic lubricants to resist chemical decomposition (hydrolysis) in the presence of water.

Hypoid gear lubricants - a special lubricants formulated to overcome the extreme pressure and sliding motion of hypoid gears found in differentials within transmission systems.

Kinematic viscosity - measure of a fluid’s resistance to flow under gravity at a specific temperature (usually 40 or 100 deg C).

Knock - noise associated with the premature ignition of the fuel-air mixture in a combustion chamber.

KOH - potassium hydroxide.

Lacquer - a thin, insoluble, non-wipeable film occurring on interior parts of compressor screws, engines etc. Can cause sticking and result in damage to mechanical components.

Lands - the circumferential areas between the groves of a piston.

Load carrying capacity - qualitative term to describe the ability of a lubricant to resist film rupture and protect against wear and surface destruction under conditions of high speeds, high loads, high temperatures or combinations of these.

Lubrication - Control of friction and wear by the introduction of a friction reducing film between moving surfaces in contact. The film may be fluid, solid or plastic.

Metal deactivator - Additive inhibiting the catalytic action of metals on the oil. Metals, particularly copper or alloys, are known to promote oil oxidation.

Moly - Prefix typically used to describe molybdenum disulphide.

Molybdenum disulphide - Chemical which has very good solid lubrication properties. Commonly used in greases and forming oils.

Morphology - The study of the form of things.

Motor octane number (MON) - The numerical indication of a gasoline's ability to prevent detonation under high speed, high load operation.

Multigrade oil - Engine or gear oil that meets the requirements of more than one SAE viscosity grade classification and can thus be used over a wider operating temperature range than a single grade oil.

Naphthenic - Petroleum fluid derived from naphthenic crude oil.. Contains a high proportion of ring molecules.

Neutral oil - The most common types of base stock used in lubricant formulations.

Neutralisation number - The measure of the acidity or alkalinity of an oil. The number is the mass in milligrams of the amount of acid (HCI) or base (KOH) required to neutralise one gram of oil.

Newtonian flow - Flow of a fluid where the shear rate (flow rate) is directly proportional to the shearing force (pressure) ie viscosity is independent of shear rate. 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 - The process whereby nitrogen oxide attacks petroleum oils at high temperatures, often resulting in viscosity increase and deposit formation.

NLGI classification number - Series used to classify the hardness/softness of grease using standard cone test.

Octane number - A measure of a fuels detonation quality in spark ignition engines as measured against reference fuels in a standard single cylinder, variable compression ratio engine.

Octane requirement (OR) - The lowest octane number reference fuel that will allow an engine to run knock free under standard conditions of service. Octane requirement is a characteristic of each individual engine.

Octane Requirement Increase (ORI) - As deposits accumulate in the combustion chamber of an engine, its octane requirement increases.

Oxidation - Petroleum oils are attacked by oxygen, accelerated by heat, light, metal catalysts and water. The result is an increase in viscosity and deposit formation.

Oxidation inhibitor - Additive added to oils to improve resistance to oxidation and increase the life of the lubricant. Another term is anti-oxidant.

Oxidation stability - Ability of a lubricant to resist oxidation and deterioration resulting from high temperatures or exposure to air.

Oxygenate - An oxygen containing, ashless organic compound such as alcohol or ether, that can be blended into gasoline to improve the octane number or reduce exhaust carbon monoxide (CO) content.

Paraffinic - Petroleum oils derived from paraffinic crude and containing a high proportion of straight chain saturated hydrocarbons.

Ping - see detonation.

Pitting - Surface cavities during rolling contact.

Poise - 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. Shear stress dynes per sq cm dynes per sq cm Viscosity = -------------- = ------------------- = ------------------- Shear rate cm/s/cm s

Polishing (bore) - Excessive smoothing of the surface finish of the cylinder bore or cylinder liner in an engine to mirror-like appearance, resulting in depreciation of ring sealing and oil consumption performance.

Positive Crankcase Ventilation (PCV) - A system for removing blow-by gases from the crankcase and returning them through the carburettor intake manifold to the combustion chamber where they are burnt. A PC valve controls the flow of gases from the crankcase to reduce hydrocarbon emissions.

Pour point - The lowest temperature at which the lubricant will flow.

Pour point depressant - Additive used to lower pour point or low temperature fluidity of a petroleum product.

Pre-ignition - 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.

Pumpability - The low temperature, low 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, including thermal cracking, catalytic cracking, polymerisation, alkylation, reforming, hydrocracking, hydroforming, hydrogenation, hydrogen treating, solvent extraction, dewaxing, de-oiling, acid treatment, clay filtration and deashphalting.

Reid vapour pressure (RVP) - Usually used in reference to motor gasolines. It is the vapour pressure of a sample at 37.8 deg C (100 deg F).

Rerefining - A process of reclaiming used lubricant oils and restoring them to a condition similar to virgin stocks by filtration, clay adsorption or more elaborate methods.

Residual fuel - Fuel composed mainly of materials remaining as unevaporated after distillation of crude oil.

Ridging - The characteristic rippled appearance on gear teeth.

Ring sticking - Freezing of a piston ring in its grove in a piston engine or reciprocating compressor 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 preening - Form of plastic flow that gives the surface a hammered appearance. The metal may be rolled over gear teeth tips.

Rust preventive - Additive which inhibits corrosion or lubricant formulated to prevent rusting of components in storage.

SAE - Society of automotive engineers.

Scratching - Fine abrasive furrows in the direction of sliding.

Scuffing - Abnormal engine wear due to localised welding and fracture. It can be prevented by the addition of anti-wear, extreme-pressure and friction modifier additives.

Shear stability index (SSI) - A measure of a viscosity modifier's contribution to an oil's percentage kinematic viscosity loss. i.e. viscosity loss x 100/polymeric viscosity thickening.

Sludge - A thick, dark residue, normally of mayonnaise consistency, that accumulates on non-moving engine interior surfaces. Generally removable by wiping unless baked hard. It's formation is associated with overload of insolubles in the lubricant.

Solvent extraction - Refining process to separate reactive components (unsaturated hydrocarbons) from lubricant distillates in order to improve the oil's oxidation stability, viscosity index and additive response.

Solvent refining - A process for extracting lubricant base stocks from stripped heavy gas oil or other heavy, stripped crude stream using selective solvents such as furfural or phenol.

Spalling - Severe damage characterised by large pits, cavities and cracks. Related to overloading 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 - Lubricants made by chemically reacting materials of a specific chemical composition to produce a compound with planned and predictable properties.

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 the 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 - The science of understanding interactions between surfaces moving against each other. Used to study lubricant interactions and influences.

USDA H-1 and H-2 - H-1 means that the products are suitable for applications where there might be incidental food contact, whereas H-2 are food grade products that should be used in areas where there is no risk of food contact.

Valve lifter - Also called cam follower. The component in engines which translates the circular motion of the cam into reciprocating motion at the valve stem.

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. Called lacquer in diesel engines.

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 to viscosity with temperature.

Viscosity modifier - Additive, usually a high molecular weight polymer, that reduces the tendency of an oil's viscosity change with temperature.

White oil - Highly refined lubricant base stock. Used for speciality applications such as cosmetics, release agents for bread in mould and medicines.

ZDDP - Zinc dialkyl dithiophosphate used as an additive for anti-wear and anti-oxidation properties in lubricants.