Why is it important not to mix turbine fuel with aviation gasoline used in an aircraft with a reciprocating engine?

• A. It will cause detonation
• B. It will improve performance
• C. It will reduce octane
• D. It will increase fuel economy

Answer: (A)

The important idea here is fuel anti-knock quality. Aviation gasoline used in piston engines is formulated with a high octane rating (and often lead additives) to resist detonation, which is the unwanted auto-ignition of the fuel–air mixture ahead of the spark. Jet fuel, used in turbine engines, has much lower anti-knock properties. When these fuels are mixed, the resulting blend loses octane and becomes more prone to detonation under normal operating conditions. That detonation can cause severe engine damage—piston crowns, bearings, and other components can be harmed by the abnormal burning. So, mixing turbine fuel with avgas creates a dangerous condition for a reciprocating engine; it won’t improve performance or economy and is unsafe because it increases the risk of detonation.