An octane rating is simply a measure of how heat resistant a fuel is in order to prevent knocking. In other words, octane doesn't enhance combustion — it prevents the air-fuel mixture inside an engine from igniting before it's supposed to. The higher a fuel's octane, the more resistant it is to knocking.

What does octane really do?

What does octane do? It just prevents the air-fuel mixture from igniting before the spark plug does it. Firing the air-fuel mixture at the proper time gives you the maximum power your engine was designed to get. Using higher-octane gasoline than your engine is designed to utilize is only wasting your money.

How is octane added to gas?

Cracking, isomerization and other processes can be used to increase the octane rating of gasoline to about 90. Anti-knock agents may be added to further increase the octane rating. Tetraethyl lead, Pb(C2H5)4, was one such agent, which was added to gas at the rate of up to 2.4 grams per gallon of gasoline.