What do 98 and 95 mean?

[LaMalia]

98 and 95 are the octane ratings of automotive gasoline. The differences between 98-octane gasoline and 95-octane gasoline are as follows: Different octane values: 98-octane gasoline is a mixture equivalent to 98% isooctane and 2% n-heptane; 95-octane gasoline consists of 95% isooctane and 3% n-heptane. Different anti-knock combustion capabilities: 98-octane gasoline has higher anti-knock performance and power output; 95-octane gasoline has average anti-knock combustion capability. Gasoline appears as a transparent, flammable liquid, refined from various petroleum-derived components such as straight-run gasoline, catalytic cracking gasoline, and catalytic reforming gasoline, blended with high-octane components. It is primarily used as fuel for spark-ignition internal combustion engines in automobiles.