Octane Ratings

Octane is the name of a compound in the alkane series (see Unit 2, Section 1) that has eight carbon atoms (C₈H₁₈). Octane is one of many hydrocarbon compounds present in gasoline.

A fuel's octane rating is a measure of its ability to resist catching on fire too soon while it is being compressed and heated in the cylinders of an internal-combustion engine. Octane ratings are sometimes called "anti-knock" ratings, because engines knock loudly when their fuel-air mixtures ignite too early. The higher a fuel's octane number, the more resistant it is to pre-ignition, and the higher the engine's compression ratio can be.