Fuel
Almost all oils burn in air generating heat, which can be used directly, or converted into other forms of fuels by various means. For example, heating water into steam which is funneled into a turbine which turns a generator, which then produces electricity. Oils are used as fuels for heating, lighting (e.g. kerosene lamp), powering combustion engines, and other purposes. Oils used for this purpose nowadays are usually derived from petroleum, (fuel oil, diesel oil, gasoline (petrol), etc), though biological oils such as biodiesel are gaining market share.

Heat transport
Many oils have higher boiling points than water and are electrical insulators, making them useful for liquid cooling systems, especially where electricity is used.

Lubrication
Due to their non-polarity, oils do not easily adhere to other substances. This makes oils useful as lubricants for various engineering purposes. Mineral oils are more suitable than biological oils, which degrade rapidly in most environmental conditions.

Painting
Color pigments can be easily suspended in oil, making it suitable as supporting medium for paints. The slow drying process and miscibility of oil facilitates a realistic style. This method has been used since the 15th century.

Petrochemicals
Crude oil can be processed into petroleum, plastics, and other substances.