text: what is oil made out of what are the elements of oil?   oils are composed of one or several liquid hydrocarbon compounds. they differ from other hydrocarbons, such as alcohols, ketones and ethers by their non-polarity. their difference from fats and waxes is given by the length of their molecule chains.  in particular, petroleum consists of a complex mixture of various hydrocarbons, largely of the alkane series, but may vary much in appearance and composition.