Motor oils, engine oils, or engine lubricants is any of various substances comprising base oils enhanced with additives, particularly antiwear additive plus detergents, dispersants and, for multi-grade oils viscosity index improvers. The main function of motor oil is to reduce friction and wear on moving parts and to clean the engine from sludge (one of the functions of dispersants) and varnish (detergents). It also neutralizes acids that originate from fuel and from oxidation, improves sealing of piston rings, and cools the engine by carrying heat away from moving parts.In addition, almost all lubricating oils contain corrosion (GB: rust) and oxidation inhibitors. Motor oils may be composed of only a lubricant base stock in the case of non-detergent oil, or a lubricant base stock plus additives to improve the oil's detergency, extreme pressure performance, and ability to inhibit corrosion of engine parts.