What fuel is commonly used in spark-ignition engines?

What fuel is commonly used in spark-ignition engines? Gasoline is the standard answer.

Gasoline, called petrol in much of the world, is formulated for engines in which an electric spark from a spark plug ignites the air-fuel mixture. This distinguishes spark-ignition engines from compression-ignition engines, such as conventional diesel engines, where heat from compressed air initiates combustion.

Gasoline is refined from crude oil and contains a blend of hydrocarbons plus additives. Its octane rating describes resistance to premature ignition, commonly called knocking. Higher-octane fuel is not automatically more powerful in every engine; it is mainly important when an engine’s design or control system requires greater knock resistance.

Gasoline is common, but it is not the only possible fuel for spark-ignition engines. Depending on the design, they can run on ethanol blends, liquefied petroleum gas, methanol, compressed natural gas, hydrogen, or other fuels. In everyday car-engine trivia, however, gasoline remains the canonical answer. Ethanol is often blended into gasoline rather than used as the only fuel.