Carbon compounds which only contain the elements Hydrogren (H) and Carbon (C) are called hydrocarbons, all of which are organic (life-related) compounds. They are often found naturally in crude oil.
Engine Uses
Hydrocarbons are used as lubricant (known as motor oil) in an engine, as well as combustable material (in the form of both gasoline and diesel). Sometimes it is found in gaskets and other sealers.

Pictured below is a representation of a Benzene (a hydrocarbon) molecule, with the Hydrogen atoms in gray and the Carbon atoms in red:
