Aviation fuel has been steadily improving, and that improvement continues today with the potential development of unleaded aviation gasoline to reduce health risks.
- Higher octane fuel allowed higher compression ratios with greater horsepower without increasing the engine size.
- In WW2, the Allies had access to relatively inexpensive 100/130 octane avgas (The first number is the lean mixture rating, the second a richer mixture).
- The Germans - 91/100 with some 95/120.
- Japan- 87/91 octane.
- Some piston engine aircraft currently use 100LL avgas containing a lead additive- an alternative is being developed.