just as a bit of fuel to the flames on this gasoline delema, as an faa aviation mechanic, first off the previous statement about cylinder heads being pulled every 100hrs, not correct, faa 100hr only is only required for comercially used airplanes, and not personal, and it does not invilve the removal of the cylinder heads , only a compression check, head removal is not an inspection but a major repair not included in 14 CFR part 43, aircraft engines operate at very high tempratures, so hot that the underside of the pistons are finned to transfer heat to the oil to prevent the burning of pistons, at these super high internal cylinder tempratures without high octane ratings the chance of detionation would be very high. aviation fuels are also rated differently than automotive, they are rated on the percentage of actual octane contained in the fuel, up to 100 percent, and anything above that figure is considered to be a performance number which is an aproximation of the extension of the octane scale, unlike automotive fuels that are rated on there actual knock resistance that is determined by a once cylinder test engine with internal cylinder pressure probes. but all in all it will not harm your engine, except for fouling the o2 sensors, it does not absorb moisture as previously mentioned, we drain the tanks becaus the chances of fuel line ice are greater than on an automotive engine and the end results more devistating, and cars have an ammount of fuel that is not usable, but airplanes recieve fuel from the tanks lowest point, so the posibility of sucking water is greater. if any engien was going to burn exhaust valves it would be an aviation engine with the super high temps, most aviation engines run sodium filled valves, do you, they have super high valves temps that the extra lead helps to prevent seat errosion, but due to the higher lead content the fuel contains additives to remove lead deposits from the cylinders, but all in all its the lead content that makes the fuel illegal for the street, and its because of the epa not its running capabilities, internal combustion engiens are all the same, especially in the same fuel catagory, if there was evwen a slight problem wth this gas, then the faa would ban it.
Grant
. As far as 100LL tearing up plugs and valves, I can say in my case that is not true. Good luck.
