Motor oil, engine oil, or engine lubricant is any one of various substances used for the lubrication of internal combustion engines. They typically consist of base oils enhanced with various additives, particularly antiwear additives, 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 and varnish (detergents). It also neutralizes acids that originate from fuel and from oxidation of the lubricant (detergents), improves the sealing of piston rings, and cools the engine by carrying heat away from moving parts.
Pouring fresh motor oil into an engine
Quart containers of branded bottled motor oil at a store
Using a funnel to assist with a motor oil refill
A woman checking a car's oil level in Togo, West Africa
Internal combustion engine
An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.
Diagram of a cylinder as found in an overhead cam 4-stroke gasoline engine: C – crankshaft E – exhaust camshaft I – inlet camshaft P – piston R – connecting rod S – spark plug V – valves. red: exhaust, blue: intake. W – cooling water jacket gray structure – engine block
Reciprocating engine of a car
Diesel generator for backup power
Bare cylinder block of a V8 engine