I'm not so sure 100 octane fuel is available any longer. It was replaced a few years back with 100 LL, which is the Low Lead variety. 80, which was tinted red, has all but gone the way of the Dodo bird. 100 LL is tinted green. There was a blue and a purple that had higher octane ratings. There is no air entrainment (sp) involved, as you gain altitude you can manually change the fuel mixture as required. Sniper