jOe wrote:All good points. Why then is this level of octane used for aviation?
I wouldn’t think airplanes have abnormally high compression (no idea ). I suspect it might have something to do with the oxygen content at altitude or ambient operating temperature.
Like others posting here, I too am not an aviator. That said, with respect to the reason for running high octane Av gas, I would think that like everything associated with aviation it is about “safety factor”. As others have noted many of the engines do not require high octane fuel and in general are relatively low compression engines, e.g., consider the Continental engines used in the ubiquitous small Cessna airplanes.
https://www.continentalmotors.aero/engines/400.aspxHowever, there is one thing an aviation engine should never do and that is to experience detonation, as detonation would be a one way street heading down, and that’s a bad direction to be heading unintentionally in an aircraft. Although high octane fuel may not be required to operate an aviation engine, it provides a significant safety margin against detonation. Air cooled aviation engines operate in a very wide range of temperatures (arctic to desert) and perhaps when you are stuck in line on the tarmack of a desert runway waiting for clearance to take off, and then experience delay after delay, you’d be glad you had a significant safety margin against detonation when you finally throttle up.