Lubricating Oil


Since the Roman era, many liquids, including water, have been used as lubricants to minimize the friction, heat, and wear between mechanical parts in contact with each other. Today, lubricating oil, or lube oil, is the most commonly used lubricant because of its wide range of possible applications. The two basic categories of lube oil are mineral and synthetic. Mineral oils are refined from naturally occurring petroleum, or crude oil. Synthetic oils are manufactured polyalphaolefins, which are hydrocarbon-based polyglycols or ester oils.

Although there are many types of lube oils to choose from, mineral oils are the most commonly used because the supply of crude oil has rendered them inexpensive; moreover, a large body of data on their properties and use already exists. Another advantage of mineral-based lube oils is that they can be produced in a wide range of viscosities—viscosity refers to the substance's resistance to flow—for diverse applications. They range from low-viscosity oils, which consist of hydrogen-carbon chains with molecular weights of around 200 atomic mass units (amu), to highly viscous lubricants with molecular weights as high as 1000 amu. Mineral-based oils with different viscosities can even be blended together to improve their performance in a given application. The common 1OW-30 motor oil, for example, is a blend of low viscous oil (for easy starting at low temperatures) and highly viscous oil (for better motor protection at normal running temperatures).

First used in the aerospace industry, synthetic lubricants are usually formulated for a specific application to which mineral oils are ill-suited. For example, synthetics are used where extremely high operating temperatures are encountered or where the lube oil must be fire resistant. This article will focus on mineral-based lube oil.

Raw Materials

Lube oils are just one of many fractions, or components, that can be derived from raw petroleum, which emerges from an oil well as a yellow-to-black, flammable, liquid mixture of thousands of hydrocarbons (organic compounds containing only carbon and hydrogen atoms, these occur in all fossil fuels). Petroleum deposits were formed by the decomposition of tiny plants and animals that lived about 400 million years ago. Due to climatic and geographical changes occurring at that time in the Earth's history, the breakdown of these organisms varied from region to region.

Because of the different rates at which organic material decomposed in various places, the nature and percentage of the resulting hydrocarbons vary widely. Consequently, so do the physical and chemical characteristics of the crude oils extracted from different sites. For example, while California crude has a specific gravity of 0.92 grams/milliliter, the lighter Pennsylvania crude has a specific gravity of 0.81 grams/milliliter. (Specific gravity, which refers to the ratio of a substance's weight to that of an equal volume of water, is an important aspect of crude oil.) Overall, the specific gravity of crudes ranges between 0.80 and 0.97 grams/milliliter.

Depending on the application, chemicals called additives may be mixed with the

Lubricating oil is refined from crude oil. After undergoing a purifying process colled sedimentation, the crude oil is heated in huge fractionating towers. The various vapors—which can be used to make fuel, waxes, or propane, among other substances—boil off and are collected at different points in the tower. The lube oil that is collected is filtered, and then additives are mixed in.
Lubricating oil is refined from crude oil. After undergoing a purifying process colled sedimentation, the crude oil is heated in huge fractionating towers. The various vapors—which can be used to make fuel, waxes, or propane, among other substances—boil off and are collected at different points in the tower. The lube oil that is collected is filtered, and then additives are mixed in.
refined oil to give it desired physical properties. Common additives include metals such as lead or metal sulphide, which enhance lube oil's ability to prevent galling and scoring when metal surfaces come in contact under extremely high pressures. High-molecular weight polymerics are another common additive: they improve viscosity, counteracting the tendency of oils to thin at high temperatures. Nitrosomines are employed as antioxidants and corrosion inhibitors because they neutralize acids and form protective films on metal surfaces.

The Manufacturing

Lube oil is extracted from crude oil, which undergoes a preliminary purification process (sedimentation) before it is pumped into fractionating towers. A typical high-efficiency fractionating tower, 25 to 35 feet (7.6 to 10.6 meters) in diameter and up to 400 feet (122 meters) tall, is constructed of high grade steels to resist the corrosive compounds present in crude oils; inside, it is fitted with an ascending series of condensate collecting trays. Within a tower, the thousands of hydrocarbons in crude oil are separated from each other by a process called fractional distillation. As the vapors rise up through the tower, the various fractions cool, condense, and return to liquid form at different rates determined by their respective boiling points (the lower the boiling point of the fraction, the higher it rises before condensing). Natural gas reaches its boiling point first, followed by gasoline, kerosene, fuel oil, lubricants, and tars.



Filtering and solvent extraction

Additives, inspection, and packaging

Quality Control

Most applications of lube oils require that they be nonresinous, pale-colored, odorless, and oxidation-resistant. Over a dozen physical and chemical tests are used to classify and determine the grade of lubricating oils. Common physical tests include measurements for viscosity, specific gravity, and color, while typical chemical tests include those for flash and fire points.

Of all the properties, viscosity, a lube oil's resistance to flow at specific temperatures and pressures, is probably the single most important one. The application and operating temperature range are key factors in determining the proper viscosity for an oil. For example, if the oil is too viscous, it offers too much resistance to the metal parts moving against each other. On the other hand, if it not viscous enough, it will be squeezed out from between the mating surfaces and will not be able to lubricate them sufficiently. The Saybolt Standard Universal Viscometer is the standard instrument for determining viscosity of petroleum lubricants between 70 and 210 degrees Fahrenheit (21 and 99 degrees Celsius). Viscosity is measured in the Say bolt Universal second, which is the time in seconds required for 50 milliliters of oil to empty out of a Saybolt viscometer cup through a calibrated tube orifice at a given temperature.

The specific gravity of an oil depends on the refining method and the types of additives present, such as lead, which gives the lube oil the ability to resist extreme mating surface pressure and cold temperatures. The lube oil's color indicates the uniformity of a particular grade or brand. The oil's flash and fire points vary with the crude oil's origin. The flash point is the temperature to which an oil has to be heated until sufficient flammable vapor is driven off so that it will flash when brought into contact with a flame. The fire point is the higher temperature at which the oil vapor will continue to burn when ignited.

Common engine oils are classified by viscosity and performance according to specifications established by the Society of Automotive Engineers (SAE). Performance factors include wear prevention, oil sludge deposit formation, and oil thickening.

The Future

The future of mineral-based lubricating oil is limited, because the natural supplies of petroleum are both finite and non-renewable. Experts estimate the total recoverable light to medium petroleum reserves at 1.6 trillion barrels, of which a third has been used. Thus, synthetic-based oils will probably be increasingly important as natural reserves dwindle. This is true not only for lubricating oil but also for the other products that result from petroleum refining.

Where To Learn More


Fuels, Lubricants, and Coolants, 7th ed. Deere & Company Service Publications, 1992.

Malone, L. J. Basic Concepts of Chemistry. John Wiley & Sons, Inc., 1989.

Nadkarni, R. A., ed. Analysis of Petroleum Products & Lubricants. American Society for Testing & Materials, 1991.

Seal, Shirley C., ed. Fluids, Lubricants & Sealing Devices. National Fluid Power Association, 1989.


Bienkowski, Keith. "Coolants and Lubricants: The Truth." Manufacturing Engineering. March, 1993.

"System Provides Real-Time Lube Oil Blending." Design News. February 26, 1990, p. 39.

O'Lenick, Anthony and Raymond E. Bilbo. "Saturated Liquid Lubricant Withstands Aluminum Forming." Research & Development. February, 1989, p. 162.

Peterson, Ivars. "Friction Features." Science News. April 30, 1988, p. 283.

Templeton, Fleur. "The Right Lube Job for Superhot Ceramic Engines?" Business Week. May 18, 1992, p. 113.

Vogel, Todd, John Rossant, and Sarah Miller. "Oil's Rude Awakening." Business Week. September 26, 1988, p. 44.

Craig F. Whitlow

User Contributions:

Per Wiklund
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May 16, 2006 @ 3:03 am
More and more lube oils are made using hydrotreatment which is not mentioned in the article. With this technolgy envirionmentally friendly production of very highly refined oil can be achieved without the use of solvent extraction. Furthermore very heavy crudes, of which there is plenty in the ground, can be utilized.
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Jul 26, 2007 @ 8:08 am
i want to know the process of refining of used oil
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Aug 12, 2007 @ 1:01 am
Could you please let me know what is the boiling point of lubricating oil?
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Apr 11, 2010 @ 2:02 am
I want to blend high performance auto motive engine oil what kind of chemicals should be added in how many percentage as an additive in base oil as well what are an important apparatus necessary to check the characteristics of lubricating oil
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Jun 23, 2011 @ 1:01 am
The diagram of the 2 distillation column is not clear enough. e. g (1)thetop product of the V.distillation column is gasoline while prpane product is the second product from the bottom?
(2)no line of lubricating oil is shown from the atms. disillation?so my questions are:
1- the products of an atmo.distillation column from the top to the bottom are,Gas,total naphtha, kerosine, LGO,HGO and residue. can you tel me from which slot we pull the lubricating oil?
2- the product of Vac. distillation column from top to bottom are: wilde distillate VLGO.VHGO and bunker fuel. can you tell me from which slot we pull lubricating oil. thank you in advance
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Aug 8, 2012 @ 9:09 am
I want to receive information on lub oil manufacturing
Want to have details on it.
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Aug 13, 2012 @ 3:03 am
It's ok, bt nt into details. Give us the details as what a chemist will carrx more reserch on. Details on the constituents of the additives used and also the diffrent kind of lubricant oil that can be produced from base oil.
Obed Mnene
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Aug 8, 2013 @ 3:03 am
I would like to know if during the refinery of oil sulfur products such as mercaptans and hydrogen disulphide are produced

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