Octane is a measure of a fuel's resistance to knocking, which is a condition that occurs when the air-fuel mixture in a gasoline engine ignites too early, causing a rapid increase in pressure and a knocking or pinging sound. The higher the octane number, the more resistant the fuel is to knocking.
Octane works by slowing down the burning rate of the air-fuel mixture in the engine. This gives the mixture more time to mix completely before it ignites, which helps to prevent knocking.
The octane rating of a fuel is determined by comparing its knocking characteristics to those of two reference fuels, isooctane and n-heptane. Isooctane is given an octane rating of 100, while n-heptane is given an octane rating of 0. A fuel with an octane rating of 87, for example, has the same knocking characteristics as a mixture of 87% isooctane and 13% n-heptane.
The octane rating of a gasoline blend is important because it determines how well the fuel will perform in an engine. A fuel with a too low octane rating can cause knocking, which can damage the engine. A fuel with a too high octane rating, on the other hand, is not necessary and will result in decreased fuel economy.
Most gasoline engines require a fuel with an octane rating of between 87 and 91. High-performance engines, however, may require a fuel with an octane rating of 93 or higher.
