AVGAS is high octane (burns slower and has higher flash point) oxygenated fuel(less oxygen in the air at high altitudes) wont mess with your jetting tho, has a HIGH lead content, the lead keeps your top end cooler and is good for your valves/cylinder(lead is like a lube) but if u run it strait all the time it builds on your plug, most avgas has a die in it to detect leaks (gas leaks in planes=bad) so if your carb overflow or petcock leaks it dies your stuff but helps find slow leaks, RACE GAS is cleaner burning than avgas and you can get it oxygenated and leaded also, but it cost alot more, look up VP race fuels, i myself would run race gas/93 pump gas(dont buy it from somewhere no body buys premium, youll get bad premium which is worst than good regular, buy from somewhere that alot boats fuel up at) mix to suit your compression, avgas is like 115 octane, 115+93=208 208/2=104, u could run that with 19cc domes(standard stroke), +banshees drink gas and avgas is cheaper, my .02