Higher compression engines have the benefit of maximizing the amount of useful energy evolved per unit of fuel. Therefore, the thermal efficiency of the engine is increased in accordance with the vapour power cycle analysis of the second law of thermodynamics.[1] The reason all engines are not higher compression is because for any given octane, the fuel will prematurely detonate with a higher than normal compression ratio. This is called preignition, detonation or knock and can cause severe engine damage.