Octane

Octane is a colorless, flammable, liquid alkane hydrocarbon with the chemical formula C₈H₁₈. It is a component of gasoline (petrol) and other fuels, contributing to their energy content. Octane exists in multiple isomeric forms, differing in the arrangement of carbon atoms within the molecule. These isomers have varying resistance to auto-ignition (knocking) in internal combustion engines.

The octane rating is a measure of a fuel's resistance to knocking. Higher octane ratings indicate greater resistance to knocking. This rating is typically determined by comparing the fuel's knocking performance to a blend of isooctane (2,2,4-trimethylpentane), which is assigned an octane rating of 100, and n-heptane, which is assigned an octane rating of 0. A fuel with an octane rating of 91 performs similarly to a blend of 91% isooctane and 9% n-heptane.

Different testing methods are used to determine octane rating, including Research Octane Number (RON) and Motor Octane Number (MON). RON is typically higher than MON. The Antiknock Index (AKI), often displayed on fuel pumps, is the average of RON and MON.

Octane is produced primarily through the refining of crude oil. It is also produced synthetically. In addition to its use in fuels, octane is used as a solvent and in the production of other chemicals.

Exposure to high concentrations of octane vapor can cause dizziness, headache, and other symptoms. It is also an environmental pollutant, contributing to air pollution and smog.