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THE MEDIA PORTAL FOR THE EUROPEAN LUBRICANTS INDUSTRY September 2017

Oil Industry Glossary of Terms

Glossary of Oil Industry Terms

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Acid Number (AN) - Milligrams of KOH required in tests to neutralise all the acidic constituents present in a 1 gram sample of petroleum product. Also formerly called the Neutralisation Number, this property is often used to indicate the extent of contamination or oxidation of used oils.

Additive - Any material that is incorporated into a product at relatively low concentration to impart new properties or enhance existing properties.

Air Release Value - The number of minutes for air entrained in oil to reduce the volume to 0.2% under the conditions of test and at the specified temperature.

Aniline Point - The minimum temperature for complete miscibility of equal volumes of aniline and the sample under test. Products containing aromatics or naphthenes have lower aniline points than products containing paraffins.

Anti-foam Agent - Additive used to suppress the foaming tendency of petroleum products in service. May be a silicone oil to break up surface bubbles or a polymer to decrease the number of small entrained bubbles.

Anti-wear (AW) Agent - Additive that is active in preventing damage caused by occurrence of solid phase welding between sliding surfaces without local surface melting.

API Gravity - Arbitrary scale expressing, in degrees API, the specific gravity of liquid petroleum products.
Degrees API = 141.5 – 131.5     sp gr 60 / 60°F

API Service Classification - System of letter designations agreed on by API, SAE and ASTM to define broad classes of engine service. Also a system of service classifications for automotive gear lubricants.

Apparent Viscosity - Measure of the viscosity of a non-Newtonian fluid under specific temperature and shear rate conditions.

Aromatic - A hydrocarbon derived from, or characterised by the presence of, the benzene ring.

Ash - Metallic deposits formed in the combustion chamber and other engine parts during high-temperature operation.

Ash (Sulfated) - see Sulfated Ash


B

Bactericide - Chemical compound which has the property of killing bacteria.

Base Number (BN) - Quantity of hydrochloric (ASTM D974) or perchloric (ASTM D2896) acid expressed in milligrams of KOH equivalent that is required to neutralise all the basic constituents of a 1 gram sample of petroleum product. This property is used to indicate the capacity of an oil to counter the corrosive effects of acidic products of combustion.

Bore Polishing - Excessive smoothing of the surface finish of the cylinder bore or liner in an engine to a mirror-like appearance. This results in the piston oil control ring being unable to control oil consumption.

Boundary Lubrication - Lubrication between two rubbing surfaces without the development of a full lubricating film. It occurs under high load and low speed, and requires the use of antiwear  or extreme pressure additives to prevent metal-to-metal contact.

BP - Abbreviation for British Pharmacopoeia usually used in reference to a purity standard for medicinal white oils, or white oils that will come into contact with foods.

Bright Stock - Refined, high viscosity lubricating oils usually made from residual stocks by suitable treatment, such as a combination of acid treatment or solvent extraction with dewaxing or clay finishing.

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

 

C

Carbon Residue - Standardised test which measures the amount of carbon left behind after pyrolysis under standard conditions.

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 - Measure of the ignition quality of a diesel fuel, as determined by a standard single cylinder test engine. The higher the Cetane Number, the easier a high speed diesel engine will start, and the less “white smoking” and “diesel knock” after start-up.

Cetane Number Improver - Additive which improves the Cetane Number of a diesel fuel.

Cleveland Open Cup (COC) Tester - Apparatus used to determine the flash and fire points of most petroleum products with flash points above 79°C.

Cloud Point - Temperature at which a noticeable cloud of crystals or other solid material appears when a sample is cooled under prescribed conditions.

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.

Complex Grease - Lubricating grease thickened by a complex soap consisting of a normal soap and a complexing agent. Use of soap complexes gives products which have higher dropping points than similar lubricants made from normal soaps.

Corrosion Inhibitor - Additive that protects metal surfaces from chemical attack by water or other contaminants.

 

D

Defoamant (Foam Inhibitor) - Additive used in lubricating oils to assist the collapse of surface layers of foam caused by agitation or the release of entrained or entrapped air.

Demulsibility - Ability of a lubricant to separate from water.

Density - The mass of liquid per unit of a substance at 15°C.

Detergency - Ability of a lubricating oil to reduce or prevent deposits formed under high temperature conditions or as a result of the action of the oil of acidic contaminants.

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

Dielectric Strength - Measure of the insulating value of an electrical insulating medium. The value depends to some extent on the test method used.

Dispersancy - Ability of an oil to disperse and suspend potential deposit-forming materials so that they can be removed from the system when the oil is drained.

Distillate Fuel - Fuel composed mainly of materials evaporated during the distillation of crude oil.

DN Factor - Old reference to define bearing speed. Corresponds to bearing bore in millimetres (D) multiplied by the speed in rpm (N). Current terminology is ndm.

Dropping Point - Temperature at which the first drop of liquid separates when a grease is heated under prescribed conditions.

 

E

Emission Control System - Any of several systems intended to reduce the amount of atmospheric pollutants released by automotive vehicles.

Emulsifier - An additive that promotes the formation of a stable emulsion, usually of oil and water.

Emulsion - Intimate mixture of two or more materials which are immiscible or partially miscible with each other. In most emulsions, one material is aqueous and the other is an oil.

End Point - The highest vapour temperature recorded during the distillation test of a petroleum product.

EP Additive - See Extreme Pressure (EP) Additive

Exhaust Gas Recirculation (EGR) - System to reduce automotive emission of nitrogen oxides (NOx). It introduces exhaust gases into the intake manifold where they dilute the air/fuel ratio. This reduces peak combustion temperatures, lessening the tendency for nitrogen oxides to form.

Extreme Pressure (EP) Additive - Chemical compound imparting extreme pressure characteristics to a lubricant with the objective of reducing wear under conditions where rubbing or sliding accompanies high contact pressures, as in heavily loaded gears, particular the hypoid type.

 

F

Fiber Grease - A grease with distinctly fibrous or stringy structure, noticeable when portions of the grease are pulled apart.

Filler - Any substance such as talc, mica or various powders, which may be added to a grease, but is not considered as being primarily intended to enhance the lubricating properties of the grease.

Film Strength - Ability of a film of lubricant to resist rupture due to load, speed and temperature.

Flash Point - The lowest temperature at which vapours rising from a sample will ignite momentarily on application of a flame under specified conditions.

Floc Point - The temperature at which a flocculent collection of wax crystals first appears when a solution of freon in oil is cooled under prescribed conditions.

FZG Load Stage - The load which can be transmitted by a pair of gears under the conditions of test and temperature in the FZG gear machine.

Gaseous Fuels - Hydrocarbon gases (methane, ethane, propane, butane) which are used as internal combustion engine fuels. There is also an increase in interest in gaseous fuels gathered from landfills and sewage treatment plants for the purposes of power generation.

 

G

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


H

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

 

I

Induction Period - The time period, in an oxidation test, during which oxidation proceeds at a constant and relatively low rate.

Insolubles - Contaminants found in used oils due to dust, dirt, wear particles or oxidation products. Often measured as pentane, toluene or benzene insolubles to characterise the nature of the insoluble material.

 

J

 

K

Kinematic Viscosity - Measure of a fluid’s resistance to flow under gravity at a specific temperature (usually 40°C or 100°C).

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

KOH - Chemical symbol for the alkaline compound potassium hydroxide.

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.

 

L

Load Wear Index - Index of the ability of a lubricant to prevent wear under applied loads as determined in the Four-Ball EP Tester.

Low Speed Pre Ignition - An abnormal combustion event, which can occur at low engine speeds in smaller, turbocharged, gasoline direct injected engines. Characterised by spontaneous ignition of the fuel that starts before the spark is generated, it creates a downward force and exerts peak pressures that can exceed 100 bar. At high loads this results in very strong knock, which in the most severe cases can result in damaged pistons, broken piston rings and bent connecting rods.

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.

 

M

Metal Deactivator - Organic type of additive having the property of suppressing the catalytic action of metal surfaces and traces of metallic materials exposed to petroleum products. The most important catalytic action is the promotion of oxidation.

MIL - Prefix designation for U.S. Military Specifications.

Moly - Commonly used abbreviation for molybdenum disulfide.

Molybdenum Disulfide - Chemical compound of molybdenum and sulfur which has excellent properties as a solid lubricant due to the type of molecular structure of the particles.

Motor Octane Number (MON) - A numerical indication of a gasoline’s ability to prevent detonation under high speed, high load engine operation.

Multigrade - An oil that meets the low temperature viscosity limits of one of the SAE W numbers as well as the 100°C viscosity limits of one of the non-W numbers.

Multipurpose Grease - Lubricating grease suitable for a variety of applications such as chassis, wheel bearings, universal joints and water pumps on automotive equipment.

Multiviscosity - See Multigrade

 

N

Naphthenic - Having the characteristics of naphthenes, which are saturated hydrocarbons containing molecules with at least one closed ring of carbon atoms.

ndm - Used to define bearing speeds . “dm” is the arithmetical mean of the outer diameter and the bore in millimetres (sometimes called the pitch diameter). “n” is the speed in rpm.

Neutralisation Number - 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 in a fluid where the shear rate (flow rate) is directly proportional to the shearing force (pressure).

NF - Abbreviation for National Formulary (U.S.), generally used in reference to requirements for the purity of white oils.

NLGI Classification Numbers - Series of numbers used to classify the consistency (hardness) of a grease, based on a standard ASTM cone penetration test..

NLGI Service Classification System - System of letter designations to define classes of automotive chassis and wheel bearing greases.

Non-Newtonian Flow - Flow in a fluid where the shear rate (flow rate) varies in relationship to the shear force (pressure). Oils containing viscosity index improvers exhibit non-Newtonian flow.

Nitration - Process whereby nitrogen oxides attack petroleum fluids at high temperatures, often resulting in viscosity increase, corrosion and deposit formation.


O

Octane Number - Term numerically indicating the relative antiknock value of a gasoline. The octane number of a petrol basically depends on its hydrocarbon composition and is improved by the addition of antiknock compounds.

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

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

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

Oxygenate - Organic compounds containing oxygen which can be blended into gasoline to improve the octane number or reduce exhaust carbon monoxide (CO) content. Alcohols and
ethers are oxygenates, some of which may be used in gasoline formulation.

 

P

Paraffinic - Having the characteristics of paraffins, saturated hydrocarbons of open chain structure.

PCV System - Abbreviation for Positive Crankcase Ventilation system, a system for internal combustion engines designed to provide positive scavenging of crankcase vapours and return
them to the intake system.

Penetration - Consistency, expressed as the distance that a standard needle or cone penetrates vertically into a sample of the material under prescribed conditions of loading, time and temperature.

Pour Point - Lowest temperature at which a liquid petroleum product will flow when it is cooled under the conditions of the standard test method.

Pour Point Depressant - An additive which lowers the pour point of petroleum products containing wax by reducing the tendency of the wax to collect into a solid mass.

Preignition - Ignition of the fuel/air mixture in a petrol engine before the spark plug fires. Often caused by incandescent deposits in the combustion chamber.

 

Q

 

R

Reid vapour Pressure (RVP) - Usually used in reference to petrol, it is the vapour pressure of a sample at 37.8°C (100°F).

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

Ring Sticking - Sticking of the piston ring in its groove, usually due to heavy deposits in the piston ring zone.

Rust and Oxidation (R&O) - Additives used to enhance the rust and oxidation resistance of oils and greases.

 

S

SAE Grade - Grade indicating the viscosity range of a crankcase, transmission or rear axle lubricant, according to systems designed by SAE.

Series 3 - Abbreviation for the discontinued Caterpillar Tractor Company crankcase oil specification “Superior Lubricants (Series 3)”.

Shear Stability - Ability of a lubricant such as a grease or VI improved oil to withstand mechanical shearing without being degraded in consistency or viscosity.

SKF Test - Any of several practical tests for greases using ball or roller bearings, developed by SKF.

Sludge - Soft deposits, usually dark coloured, formed in lubrication systems, mainly consisting of oxidised lubricating oil components, water and, in internal combustion engines, carbonaceous residues from fuel combustion.

Smoke Point - Term numerically indicating the burning characteristics of kerosene or aviation turbine fuels.

Soap - General term for the “salt” of a fatty acid. Ordinary washing soaps are those of sodium and potassium. Soaps of lithium, sodium, calcium, barium and aluminum are the principal thickeners used in grease making.

Solvent Neutral Oil (SNO) - Base oil manufactured from solvent refined paraffinic lube distillates.

Spindle Oil - Low viscosity oil for the lubrication of high speed spindles such as those used in textile mills.

Straight Mineral - Oils which do not contain compounds or “additives”.

Sulfated Ash - Residue that remains after a sample of oil has been oxidised under prescribed conditions and the resulting residue reduced to a constant weight by heating with sulphuric acid. Used as a measure of the amount of metallo-organic additives present in new oils. In used oils, the determination may be affected by the presence of incombustible contaminants such as lead alkyls, dust and wear metals.

Sulfurised Oil - An oil in which elemental sulfur is either loosely combined with the oil, or is combined with a fatty oil and added to the oil. Used in applications where reactive sulphur is desired to provide extreme pressure characteristics, such as in gear oils and cutting oils.

Supplement 1 - Abbreviation for obsolete military specification US Army 2-104B (Supplement 1).

Synthetic Lubricant - Lubricant made chemically by reacting materials of a specific chemical composition to produce a compound with planned and predictable physical and chemical properties.

 

T

Tailings - In mining, the residue materials leftover from the process of separating the valuable materials from a mineral ore.

Thermal Stability - Property of a fuel or lubricant which indicates its ability to resist cracking and decomposition on prolonged exposure to elevated temperatures.

Thickener - Solid particles which are uniformly dispersed to form the structure of a grease in which the liquid lubricant is held.

Timken OK Load - Maximum load a lubricant will withstand without failure due to breakdown of the lubricant film, as determined on the Timken EP Lubricant Tester.

Typical Test - Test results that are characteristic of a product, normally mean values obtained from analysis of a number of production batches of that product.

 

U

USP - Abbreviation for U.S. Pharmacopoeia, usually used in reference to purity standard for
medicinal white oils, or white oils that will come in contact with food.

 

V

Viscosity - Measure of the resistance to flow, or internal friction, of a fluid. Viscosity changes with temperature so the temperature at which the measure has made must always be specified. See also Apparent Viscosity, Kinematic Viscosity.

Viscosity Index (VI) - An arbitrary scale used to show the relative magnitude of viscosity changes with temperature. Higher VI oils have less change in viscosity with temperature.

Viscosity Index Improver (VII) - Lubricant additive, usually a high molecular weight polymer, that reduces an oil’s tendency to change viscosity with change of temperature.

 

W

Wetting Agent - Compound having the property of modifying the characteristics of the contact between a liquid and a solid surface to promote more rapid and complete wetting of the surface.

Worked Penetration - Penetration of a sample of grease immediately after it has been brought to 25°C and worked 60 strokes in the ASTM grease worker.

 

X

 

Y

 

Z

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