gasoline

Gasoline is a highly volatile flammable liquid fuel used primarily in internal combustion engines of light-duty vehicles. It is a refined product derived from crude oil, composed of a complex mixture of hydrocarbon molecules including paraffins, cycloalkanes, and aromatics, typically in the C4 to C12 range. The exact composition varies by refinery and season. In North America the term is gasoline, while in many other regions the fuel is referred to as petrol.

Gasoline is produced by fractional distillation and refining of crude oil, followed by blending with additives to achieve desired vapor pressure, stability, and anti-knock properties. The octane rating indicates resistance to premature ignition; higher octane gasoline is used in higher-compression engines. Gasoline may be labeled with an octane number (e.g., 87, 91).

Detergents and antioxidants are commonly added; in some regions ethanol is blended (E10, E15, or E85) to reduce emissions and promote oxygen content. Leaded gasoline has been largely phased out due to health and environmental concerns; MTBE and other oxygenates have also been restricted in some areas.

Combustion emits CO2, NOx, carbon monoxide, and volatile organic compounds; evaporative losses can release vapors. It is highly flammable and presents risks of fire or explosion; proper storage, handling, and ventilation are important.

Gasoline powers most spark-ignition engines in light-duty vehicles. In some regions, fuel alternatives include diesel, natural gas, or electric propulsion; ongoing policy shifts aim to reduce gasoline use to mitigate climate change.