Motor Oils

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Motor Oils


a group of oils used to lubricate piston and jet internal-combustion engines; they belong to the class of lubricating oils. Virtually all motor oils are products of petroleum processing, and only some types of aviation oils are synthetic oils. All motor oils, with the exception of some aviation oils, contain detergents and antiwear and antioxidation additives. Cold-climate, winter, and all-season oils, produced from low-viscosity stock, also contain thickening additives and pour-point depressants, which lower their solidification temperature.

A distinction is made among automobile oils (for carburetor engines), diesel oils, and aviation oils, depending on the intended use. The first two classes, including automobile and tractor oils, as well as diesel-locomotive and marine oils, are in turn divided into 11 groups according to viscosity (at 100°C) and into nine groups according to performance characteristics (GOST [All-Union State Standard] [17–479–72).

The design features of the engine, the season, and the geographic area (north or south) determine the viscosity (6, 8, 10, 12, 14, 16, or 20 centistokes at 100°C) and pour point (from —15° to —42°C) of motor oils, and the quality group is chosen according to the type of duty (see Table 1). An increase in the quality of motor oils from group A to group F (arbitrary classification) is achieved mainly through an increase of the concentrations of additives and, in some cases, by changes in the quality of the base oil. The physicochemical properties of oils of each class and group must satisfy technical conditions; the performance characteristics are determined by tests in single-cylinder installations and test engines.

Table 1. Groups of automobile and diesel oils for various types of engines (according to GOST 17479–72)
Group ANonsupercharged carburetor and diesel engines
Group B
 B1Low-supercharged carburetor engines
 B2Low-supercharged diesel engines
Group C
 C1Medium-supercharged carburetor engines
 C2Medium-supercharged diesel engines
Group D
 D1Highly supercharged carburetor engines
 D2Highly supercharged diesel engines
Group EHighly supercharged heavy-duty diesel engines
Group FLow-speed diesel engines operating on heavy fuel with a sulfur content of up to 3.5 percent

Aviation motor oils are used in piston, turbojet, and turboprop engines. There are about 20 types and brands of aviation oils, from the lightest distillate type (with a viscosity of 3–4 centistokes at 100°C) to heavy residual types (with a viscosity of 22 centistokes at 100°C). The requirements for quality of aviation oils are particularly stringent. Almost all oils for jet aviation contain combinations of additives and have relatively narrow fractional composition, low pour point (from —55° to —60°C), high stability, low foaming, and good pumping characteristics in the circulation system of the motor.

In connection with the development of supersonic aviation and increased requirements for thermal stability and low-temperature properties of lubricating oils, synthetic oils have come into widespread use. Their production is based on the use of organic esters and alcohols and organosilicon and fluorocarbon compounds, as well as on extensive chemical processing of petroleum fractions and other types of raw materials. The application of such oils extends the useful temperature range of lubricating oils from —60° to + 250°C (the range for the best hydrocarbon oils is —40° to + 150°C). Synthetic oils are also used in some gas turbines and other types of motors on the ground.


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Tovarnye nefteprodukty, ikh svoistva i primenenie: Spravochnik. Edited by N. G. Puchkov. Moscow, 1971.
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Gol’dberg, D. O., and S. E. Krein. Smazochnye masla iz neftei vostochnykh mestorozhdenii. Moscow, 1972.
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