Octane (Petroleum) The numbers (87, 89, 91 etc.) refer to the octane rating, a measure of a gasoline’s resistance to detonation. Your engine uses a spark to ignite a mixture of gasoline and air, which is supposed to combust in an orderly fashion. Sometimes the heat and compression can cause pockets of fuel to explode before they are supposed to; that’s detonation (also known as knocking for the sound that it makes). The higher the octane, the more resistant the fuel is to detonation.
Most engines are designed to run on regular (87 octane) gasoline, but some cars use high-compression engines, which squeeze the air-fuel mixture down to a smaller size before igniting it with a spark. These engines are more prone to detonation, so they often require premium fuel to work most efficiently — 91 or 93 octanes.
In the past, running 87 octane fuel in a car that required premium would cause the engine to “knock” and could lead to severe engine damage. Today’s cars have knock sensors that can detect detonation and recalibrate the engine to compensate, although the engine will produce less power and may get worse gas mileage. If your car requires premium fuel, using gasoline with too low an octane rating can potentially cause damage and may void your