Is every one using 91 octan fuel

ImportConvert

The lowest octane that allows full engine timing under load without any pre-detonation will give optimal performance. All a high octane rating means is that ingredients are added to the gas which retard combustion. It's just extra material in the fluid by volume that takes away from its ability to power your car, once you reach the above point. Kindof like Ethanol, except E85 tuned cars can run some sick compression numbers and make a lot more power.