Glossary Pelumas

  Glossary Pelumas


  • Acid Number (AN) – Milligrams of KOH required in tests to neutralize all the acidic constituents present in a 19 sample of a petroleum product. Also formerly called the Neutralization 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.


  • Antifoam Agent – An 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.
  • Antiwear (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 – An arbitary scale expressing, in degrees API, the specific gravity of liquid petroleum products. Degrees API = 141.5 – 131.5 spgr60/60 oF


  • API Service Classification – A 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.


  • Ash – Metallic deposits formed in the combustion chamber and other engine parts during hightemperature operation.


  • Ash (Sulfated) See Sulfated Ash


  • Base Number (BN) – Quantity of hydrochloric (ASTM D974) or perchloric (ASTM D2896) acid expressed in milligrams of KOH equivalent that is required to neutralize all the basic constituents of a 19 sample of a petroleum product. This property is used to indicate the capacity of an oil to counter the corrosive effects of acidic products of combustion.


  • 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.


  • Complex Grease – A lubricating grease thickened by a complex soap consisting of a normal soap and a complexing agent. The use of soap complexes gives products which have higher dropping points than similar greases made from normal soaps


  • Corrosion Inhibitor – An additive which protects metal surfaces from chemical attack by water or other contaminants.


  • 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 – Property of a lubricant to separate from water.


  • Density – The mass of liquid per unit of volume of a substance at 15°C.


  • Detergency – Property of a lubricating oil to reduce or prevent deposits formed under high temperature conditions or as a result of the action on the oil of acidic contaminants.


  • Dispersancy – Property 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.


  • 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.


  • EP Additive – See Extreme Pressure (EP) Additive


  • 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, particularly of the hypoid type.


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


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


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


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


  • MIL – Prefix designation for U.S. Military Specifications.


  • Multigrade – See Multi viscosity


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


  • NLGI Service Classification System – A system of letter designations to define classes of automotive chassis and wheel bearing greases.


  • Octane Number – A term numerically indicating the relative antiknock value of a gasoline. The octane number of a gasoline basically depends on its hydrocarbon composition and is improved by the addition of antiknock compounds.


  • Oxidation Stability – Ability of a lubricant to resist oxidation and deteriozation 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.


  • Paraffinic – Having the characteristics of paraffins saturated hydrocarbons of open chain structure.


  • 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.


  • Reid Vapor Pressure (RVP) – Usually used in reference to motor gasolines, it is the vapor 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 a 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.


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


  • Shear Stability – Ability of a lubricant such as a grease or Vl improved oil to withstand mechanical

shearing without being degraded in consistency or viscosity.


  • Sludge – Soft deposits, usually dark colored, formed in lubrication systems, mainly consisting of oxidized lubricating oil components, water and, in internal combustion engines, carbonaceous residues from fuel combustion.


  • Smoke Point – A 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. The soaps of lithium, sodium, calcium, barium and aluminum are the principal thickeners used in grease making.


  • 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.


  • Thermal Stability – The property of a fuel or lubricant which indicates its ability to resist cracking and decomposition on prolonged exposure to elevated temperatures.


  • Thickener – The solid particles which are unifonnly dispersed to form the structure of a lubricating 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 which are characteristic of a product, normally mean values obtained from analysis of a number of production batches of that product.


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


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


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