Additive : Any material added to a base oil to change its properties, or performance.
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.
Ash : Metallic deposits formed in the combustion chamber and other engine parts during high temperature operation.
Ash (sulphated) : The ash content of oil, determined by charring oil, treating the residue with sulphuric acid, and evaporating to dryness. Expressed as % by mass.
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 lubrication oil additives to neutralise acids formed during the combustion of fuel or oxidation of the lubricant.
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.
Carbon residue : Coked material remaining after oil has been exposed to high temperatures under controlled conditions.
Centistokes : Measurement unit of kinematic viscosity of a fluid. One centistokes equals 0.01 Stokes and is equivalent to one mm2/sec in SI units.
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.
Copper strip corrosion : A qualitative measure of the tendency of a petroleum product to corrode pure copper.
Demulsibility : A measure of a fluid's ability to separate in water.
Density : Mass per unit volume.
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.
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.
Gravity : In petroleum products, the mass/volume relationship expresses as:
Specific gravity : specific gravity = (mass/unit volume of product @ 15°C ) divided by (mass/unit volume of water @ 15°C )
Hydro finishing : A process for treating raw extracted base stocks with hydrogen to saturate them for improved stability.
Inhibitor : Additive that improves the performance of a petroleum product by controlling undesirable chemical reactions. i.e. oxidation inhibitor, rust inhibitor.
Insolubles : Contaminants found in used oil due to dust, dirt, water, wear particles or oxidation products. Often measured as pentane or benzene insolubes to reflect insoluble character.
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.
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.
Neutral oil : The basis of most commonly used automotive and diesel lubricants, they are light overhead cuts from vacuum distillation.
Nitration : The process whereby nitrogen oxides attack petroleum fluids at high temperatures, often resulting in viscosity increase and deposit formation.
Oxidation : Occurs when oxygen attacks petroleum 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.
Pour point : An indicator of the ability of an oil or distillate fuel to flow at cold operating temperatures. It is the lowest temperature at which the fluid will flow when cooled under prescribed conditions.
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, including thermal cracking, catalytic cracking, polymerization, alkylation, reforming, hydrocracking, hydro forming, hydrogenation, hydrogen treating, solvent extraction, dew axing, de-oiling, acid treating, clay filtering and deasphalting.
Re-refining : A process of reclaiming used lubricant oils and restoring them to a condition similar to that of virgin stocks by filtration, clay absorption, solvent extraction and other elaborate methods.
Sludge : A thick dark residue that accumulates on non-moving engine interior surfaces. Generally removable by wiping unless baked to a carbonaceous consistency, its formation is associated with insolubles overloading the lubricant.
Solvent extraction : Refining process used to separate reactive components (unsaturated hydrocarbons) from lubricant distillates in order to improve the oil's oxidisation stability, viscosity index and additive response.
Solvent refining : A process for extracting lubricant base stock from stripped heavy gas oil or other heavy, stripped crude stream using selective solvents such as furfural or phenol.
Viscosity : A measure of a fluid's resistance to flow.
Viscosity index : Relationship of viscosity to the temperature of a fluid. It is determined by measuring the kinematic viscosities of the oil at 40°C and 100°C and using the tables or formulae included in ASTM D 2270. High viscosity index fluids tend to display less change in viscosity with temperature than low viscosity index fluids.
Viscosity modifier : Lubricant additive, usually a polymer, whose function is to provide beneficial rheological properties to lubricating oils, such as reducing the tendency of an oil's viscosity to change with temperature.
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