Originally Posted by Sibze

The idea of octane level:

Octane delays the ignition of the fuel. So if you have 87 octane in a car it will ignite sooner than if you have 91 in a car or 94...

The lower octane level you CAN run in a car the more performance you get because the fuel is igniting sooner. However engines like ours need to build up enough pressure before the fuel can ignite and therefore our cars need 91 octane. If you put 87 in our car the fuel will ignite too soon and cause knocking and if you put 94 in the car, the fuel is not igniting at the prime time I.E its actually delaying ignition.