Page "Motor oil" Paragraph 3

Motor oil is a lubricant used in internal combustion engines.

These include motor or road vehicles such as cars and motorcycles, heavier vehicles such as buses and commercial vehicles, non-road vehicles such as go-karts, snowmobiles, boats ( fixed engine installations and outboards ), lawn mowers, large agricultural and construction equipment, locomotives and aircraft and static engines such as electrical generators.

In engines, there are parts which move against each other causing friction which wastes otherwise useful power by converting the energy to heat.

Contact between moving surfaces also wears away those parts, which could lead to lower efficiency and degradation of the engine.

This increases fuel consumption, decreases power output and can lead to engine failure.