Octane

The octane number, or octane rating, measures gasoline’s ability to resist knocking when ignited in an air-fuel mixture in the cylinder of an internal combustion engine. Gasoline’s octane rating influences a vehicle’s fuel efficiency and exhaust emissions. Generally, when the octane number increases, the engine’s hydrocarbon and carbon monoxide emissions reduce, but nitrogen oxide emissions increase.

Vehicles are usually designed for a specific gasoline octane rating. When vehicles are designed to run on a lower-octane fuel, using a higher-octane gasoline will not provide any benefits. However, the availability of high-octane gasoline is expected to lead to more efficient engine design with higher compression rates. In the long run, this will result in lower carbon dioxide emissions