Glossary of Lubricant Terminology

A chemical added in small quantities to a base fluid in order to improve specific properties of the lubricant such as fluid life, lubricity, wear protection, rust protection, etc...

An additive that causes foam to dissipate more rapidly. It promotes the combination of small bubbles into large bubbles which burst more rapidly.

A chemical added in small quantities to a petroleum product to increase its oxidative resistance in order to prolong its service life.

An additive that minimizes wear caused by metal-on-metal contact by forming a film on the metal surfaces, typically activated by heat and pressure.

Minimum temperature at which a combustible fluid will burst into flame without the assistance of an extraneous ignition source. This temperature is typically several hundred degrees higher than the flash and fire point.

Base stocks or blends used as an inert ingredient in the manufacturing of automotive and industrial lubricants.

Refined petroleum oils that can either be blended with one another or supplemented with additives to make lubricants.

A form of lubrication effective in the absence of a full fluid film. Made possible by the inclusion of certain additives in the lubricating oil that prevent excessive friction and scoring by forming a film whose strength is greater than that of oil alone. These additives include oiliness agents, compounded oils, anti-wear agents, and extreme pressure agents.

Coked material formed after lubricating oil has been exposed to high temperatures. Many consider that the type of carbon found is of greater significance that the quantity.

A lubricant's ability to separate from water.

An additive which chemically neutralizes acidic contaminants in the oil before they become insoluble and fall out of the oil, forming sludge. Particles are kept finely divided so that they can remain dispersed throughout the lubricant.

Describing a state of an immiscible fluid component. Minute quantities of a fluid (typically water) can be dissolved or absorbed into the oil, but excess quantities can be most harmful to equipment due to the entrainment leaving gaps in the lubricated areas.

Lowest temperature at which a combustible fluid will burst into flame in the presence of an extraneous ignition source. Very little additional heat is required to reach the fire point from the flash point.

Lowest temperature at which vapor from a sample of a petroleum product or other combustible fluid will "flash" in the presence of an ignition source. The flash can be seen in the form of a small spark over the liquid.

An additive which causes foam to dissipate more rapidly. It promotes the combination of small bubbles into large bubbles which burst more easily.

A possible reaction of an oil when mixed with air. This entrained air can result in reduced film strength and a performance reduction.

Two test procedures on the same principle. The Four Ball Wear Test is used to determine the relative wear-preventing properties of lubricants operating under boundary lubrication conditions. the Four Ball Extreme Pressure Test is designed to evaluate performance under much higher unit loads.

Resistance to motion on a surface or by a substance as a result of its contact with another surface or substance. Sliding friction is that which occurs between two solid bodies, while fluid friction is that which occurs between the molecules of a fluid in motion. Both types of friction can be wasteful in power and energy, and sliding friction causes wear.

A type of lubricant composed of a fluid (typically lubricant oils) thickened with a material that contributes a degree of plasticity (typically soaps). Just as viscosity is the basic property of lubricating oil, consistency is the basic property of grease. Consistency is measured in terms of penetration, tested in terms of tenths of a millimeter that a standard cone acting under the influence of gravity penetrates the sample under controlled test conditions. the greater penetration, the softer the grease.

A Gulf patented process used to make lubricant base stocks. In the process, lubricant feedstocks are reacted with hydrogen in the presence of a catalyst at very high temperature (800°F) and pressure (3200psig). The process displaces impurities and unsaturated hydrocarbons.

Compounds of hydrogen and carbon of which petroleum products are typically examples. Petroleum oils are generally grouped into two parts: Napthenics, which possess a high proportion of unsaturated cyclic molecules; and paraffinic, which possess a low proportion of unsaturated cyclic molecules.

A type of lubrication effected solely by the pumping action developed by the sliding of one surface over another in contact with an oil. Adhesion to the moving surface draws the oil into the high-pressure area between the surfaces, and viscosity retards the tendency to squeeze the oil out. If the pressure developed by this action is sufficient to completely separate the two surfaces, full-fluid-film lubrication is said to prevail.

A form of chemical deterioration to which all petroleum products are subject to, and involves the addition of oxygen atoms resulting in degradation. It is accelerated by higher temperatures above 160°F, with the rate of oxidation doubling by each 20° increase. With fuels and lubricant oils, oxidation produces sludges, varnishes, gums, and acids, all of which are undesirable.

Resistance of a petroleum product to oxidation, therefore increasing its potential service or storage life. Since the life of many lubricants can be well over a year, simulations are used to show the time required for a sample to develop a specified degree of oxidation under accelerated conditions.

A widely used low temperature flow indicator, depicted as 5°F above the temperature to which a normal liquid petroleum product maintains fluidity. It is a significant factor in cold weather start-up.

A lubricant additive for protecting ferrous (iron and steel) components from rusting caused by water contamination or other harmful materials from oil degradation. Some rust inhibitors operate similarly to corrosion inhibitors by forming inert films on metal surfaces. Other rust inhibitors absorb water by incorporating it into a water-in-oil emulsion so that only oil touches the metal surfaces.

A unit of frictional force overcome in sliding one layer of fluid along another. This is typically measured in pounds per square foot, with pounds representing the frictional force, and square feet representing the area of contact between the sliding layers.

The collective name for contamination in an lubricated system and on parts bathed by the lubricating oil. This includes decomposition products from the fuel, oil, and particulates from sources external to the system.

The ability to dissolve into a solution producing a homogeneous physical mixture. The degree of solvency varies along with the rate of dissolution depending on the amount of heat added to the solution.

The measure of a liquids volatility. The higher the pressure at a standard test temperature, the more volatile the sample, and the more readily it will evaporate.

A deposit resulting from oxidation and polymerization of fuels and lubricants. Similar to but softer than lacquer.

Measure of a fluid's resistance to flow. This is typically measured as the time required for a standard quantity of fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid. Viscosity varies inversely with temperature so the measurements are always expressed together. Tests are typically conducted at 40°C and 100°C.

The measure of the rate of change of viscosity with temperature. Heating tends to make lubricants thinner, cooling makes them thicker. The higher the viscosity index is on a particular fluid, the less of a change in viscosity there will be over a given temperature range. In determining the viscosity index, two temperatures of viscosity are taken, one at 40°C and the other at 100°C.

The property of a liquid that defines its evaporation characteristics. Of two liquids, the more volatile will boil at a lower temperature and will evaporate faster when both liquids are at the same temperature. The volatility of petroleum products can be evaluated by tests for flash point, vapor pressure, distillation, and evaporation rate.