To understand octane rating, you need to understand a little bit about how car engines work. To control the explosions, the gasoline must burn at exactly the right rate. This is controlled by the gasoline s chemical composition.
Gasoline is a mixture of many chemicals that burn at different rates.
One chemical that burns at the right rate is isooctane. A chemical that burns too quickly is n-heptane. To describe how fast a gasoline burns, a scale was developed using these two chemicals. Isooctane is defines to have an octane rating of 100, which n-hepatine has an octane rating of 0. Octane ratings compare the burning characteristics of gasoline to mixtures of isooctane and n-hepatane.