Octane fuel is a type of gasoline that has been specifically formulated to increase its resistance to detonation or pre-ignition. This means that it is less likely to explode before the spark plug fires, which can cause engine knocking and reduce performance. The term "octane" refers to the rating system used to measure a fuel's ability to resist igniting before the spark plug fires. Higher octane fuels are more expensive because they require special refining processes that remove impurities that could cause pre-ignition.