Valve Seat Recession
Throughout the debate on eliminating leaded fuel, the focus has always been on what lead does for octane which is clear cut and well established. However, lead has also been found to protect valves and seats against valve seat recession. Some people deny that there is any benefit to using lead other than its ability to enhance octane, but this is not the case. Particularly in older designs, the small Continentals, Franklins, and in all radial engines, lead is necessary to prevent valve seat recession. Without it they may last as little as 30 hours. So while most of us are thinking about replacing octane, someone needs to be thinking about preventing valve seat recession unless we are ready to retire a large number of airplanes when 100LL is eliminated.