What defines the performance rating of aviation fuels above grade 100?

The performance rating of aviation fuels above grade 100 is defined in relation to the engine's power available compared to pure iso-octane. Aviation fuels are often measured using the octane rating system, which indicates their ability to resist knocking or pinging during combustion—a critical factor in high-performance aviation engines. A rating above 100 signifies that the fuel has superior anti-knock properties compared to iso-octane, which is the standard reference component with an octane rating of 100.

In the context of aviation, fuels with a performance rating over 100 are typically designed for high-compression engines, providing enhanced power and efficiency. This means that pilots and engineers can expect better engine performance when using fuels with these higher ratings, making them essential for advanced aircraft that require more robust fuel characteristics to operate effectively in demanding conditions.

Contamination with other fuel types, color and clarity of the fuel, and altitude effectiveness don't directly correspond to the performance rating above grade 100 in the same manner as the comparison to iso-octane, which is central to understanding fuel performance in aviation contexts.