Octane ratings represent the fuel's ability to resist pre-ignition (also known as 'knocking'). Commonly referred to as the Research Octane Number (RON), the higher the octane number, the better it prevents knocking. Most cars run on 95 octane petrol, but some cars need higher octane fuel (98) because it runs on a higher-compression gasoline engine which yields more power. To find out which octane petrol you should use - check your car's user manual to find out the recommended octane petrol for your car.