Which of the following compounds determines the octane rating of petrol?

The compound that determines the octane rating of petrol is 2,2,4-trimethylpentane. Octane rating is a measure of a fuel's ability to resist "knocking" during combustion, caused by the air/fuel mixture detonating spontaneously in the engine. The higher the octane rating, the more resistant the fuel is to knocking. The octane rating of a fuel is determined by comparing its performance to that of a mixture of 2,2,4-trimethylpentane and n-heptane, which are assigned octane ratings of 100 and 0, respectively. Therefore, 2,2,4-trimethylpentane is used as a standard reference for octane rating, and is one of the compounds that determines the octane rating of petrol.