I might have missed it but I don't recall seeing any information to support this. Please point me to it if I am mistaken. Sorry for doubting you if that is the case.
Airplanes have to take off and land so the fuel must perform at all elevations. Not just high in the air. Not all airplanes are air cooled either.
There might be other reasons that 100LL would not be a good fit for your application.