I would say the correct answer is "octane". It is important that you use the fuel with the correct octane rating recommended by the manufacturer. Among the choices it is only octane that is used as a rating for fuels. Hope this helps.
Octane rating is the fuel’s ability to resist “knocking” during combustion. Octane rating depends on what is recommended for your car’s engine by the manufacturer. For example, in the United States, the regular unleaded gasoline has typical octane ratings of between 87 (regular) to 90 (mid-grade). This is the cheapest and most standard option at the pump. The octane rating on gasoline pumps is prominently displayed on a yellow background in large black numbers. To help yourself determine your vehicle’s octane rating, always read the car’s manual to see the recommendations of the manufacturer.
