> Meanwhile, Teledyne Continental Motors indicates (in document X30548R3 most recently revised in 2008) that leaded avgas is required in their engines: "Current

> Meanwhile, Teledyne Continental Motors indicates (in document X30548R3 most recently revised in 2008) that leaded avgas is required in their engines: "Current aircraft engines feature valve gear components which are designed for compatibility with the leaded ASTM D910 fuels. In such fuels, the lead acts as a lubricant, coating the contact areas between the valve, guide, and seat. The use of unleaded auto fuels with engines designed for leaded fuels can result in excessive exhaust valve seat wear due to the lack of lead with cylinder performance deteriorating to unacceptable levels in under 10 hours." https://en.wikipedia.org/wiki/Avgas https://en.wikipedia.org/wiki/Avgas Aviation moves very slowly because of the safety and reliability requirements. This is a blessing and a curse as far as things like that go. Generally speaking, equipment gets certificated under very specific conditions and deviating from those conditions is strongly discouraged (if nothing else, by your insurer). If the POH (Pilot Operating Handbook) says that your 1967 Cessna 172 has to run on 100LL, you run 100LL and not some unleaded 100-octane equivalent. I don’t have the exact numbers, but outside of doctors and nouveau-riche tech folks, I would suspect that most of the North American GA (general aviation) fleet is 30-40 years old. There’s new GA aircraft coming to market, but they’re eye-wateringly expensive compared to perfectly serviceable older aircraft that can get an electronics upgrade.