Motor oil, engine oil, or engine lubricant is any of various substances consisting of base oils enhanced with various additives, particularly antiwear additives, detergents, dispersants, and, for multi-grade oils, viscosity index improvers. Motor oil is used for lubrication of internal combustion engines. 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 of the lubricant (detergents), improves sealing of piston rings, and cools the engine by carrying heat away from moving parts.Engine oil creates a separating film between surfaces of adjacent moving parts to minimize direct contact between them, decreasing frictional heat and reducing wear, thus protecting the engine. Single grade engine oil viscosity grades are 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60.