What do 95, 92, and 98 mean?

[McBarrett]

Gasoline grades 92, 95, and 98 represent different levels of isooctane content in the fuel, while the quality of the gasoline and the heat value per unit volume remain the same. Octane Rating: The numbers indicate the octane rating of the gasoline. The higher the number, the higher the octane rating, which means better anti-knock performance. For example, 92-grade gasoline has an octane rating of 92%, 95-grade has 95%, and 98-grade has 98%. Anti-Knock Performance: When the air-fuel mixture is injected into the cylinder, the piston moves upward to compress the mixture. As pressure increases, so does temperature. If the gasoline's anti-knock performance is too low, the mixture may start burning before the spark plug ignites it, leading to knocking (commonly known as engine knock). Higher octane ratings provide better anti-knock performance, reducing potential damage to the engine.