What are the differences between 95 and 98 octane gasoline?

Gasoline with an octane rating of 98 is more resistant to self-ignition than gasoline with an octane rating of 95. 98-octane gasoline is generally thought to give more power than 95-octane gasoline. However, an engine designed for 95-octane gasoline, with the average passenger car characteristics (e.g. acceleration from 0 to 100 km/h in about 10 secs or less) will not have more power with 98-octane gasoline; however, a high-performance sports engine will not be able to develop its full power if it runs on gasoline with a lower octane rating that is not able to sustain the high pressure and rpm of such engine types.

Therefore, a higher octane number does not imply more power—since power is conditioned by the engine’s design characteristics—but only a more efficient performance at higher rpm.