Something to know and remember: 100LL has four times the lead that 80 did, and 80 was pretty close to the old leaded Mogas. That extra lead causes much faster sparkplug fouling in aircraft engines designed to run on 80, and it doesn't do the oil much good, either. Converted auto engines could suffer the same way, especially if they're liquid-cooled. Straight 100 (the green stuff) had eight times the lead of 80. Don't see it or 80 anymore. Once in a while I'll hear of some airport having 80, but it would be rare. What refinery is going to bother with such tiny volumes?