I think some of you may be shooting from the hip here. Av gas, 100LL is a fine fuel for automotive use as long as your compression is no higher than 11.5:1. Just make sure you jet your carb accordingly. You will definetely need to richen your jetting to assure your not running lean. I do have an FAA A&P mechanics License, and am an FAA Safety Inspector, since you asked. But this has nothing to do with why I say av gas is perfectly safe for automotive use. An aircraft engine is much the same as an automotive engine and the pistons are nothing exotic either. I have used a 50/50 mix of AV gas 100LL and 111/112 octane race gas in my 12:1 car and my ET and MPH is slightly better than straight race gas. I have used straight 100LL with good results without any noticable detonation, but I think 12:1 may need higher octane just to be safe. Even though they call it 100LL it is actually a higher octane than 100 octane automotive gas as they rate it differently. Many aircraft owners use automotive pump gas in their aircraft because it is cheaper and most aircraft engines have lower compression than automotive engines. The use of automotive gas in many aircaft has been approved by the FAA. As long as your jetted correctly your safe. I have a friend that ran av gas in his GTO for may years, over 30,000 street miles and 100's of 12 second and 11 second runs at the drags with cast pistons and never had a problem. I am not sure about his compression but it was too high to run the 92 pump gas, I think around 11:1 or so. Yes av gas is oxygenated but so is pump gas. Any fuel will burn pistons if you run it too lean.
Tim C
65 LeMans, 3500lb. D-ports and a flat tappet cam, 10.92@120
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Tim Corcoran
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