Engine oil (or engine lubricant) consists of various substances used for the lubrication of internal combustion engines. They typically consist of base oils with various additives to enhance the protective performance. During manufacture anti-wear additives, detergents, dispersants, and, for multi-grade oils, viscosity index improvers are added to the base oil. The main function of engine motor oil is to reduce the amount of friction and wear on moving parts and to clean the harsh environment of the engine internals from sludge (one of the functions of dispersants) and varnish (detergents).