Octane rating or octane number is a standard measure of the performance of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating. In broad terms, fuels with a higher octane rating are used in high-compression engines that generally have higher performance. In contrast, fuels with lower octane numbers (but higher cetane numbers) are ideal for diesel engines. Use of gasoline with lower octane numbers may lead to the problem of engine knocking.