I've been maintaining aircraft and engines since 1966. There are too many details concerning the differences between 100LL Avgas and automotive fuels. Suffice it to say running 100LL will not break a valve, but Avgas burns slower than automotive gas. For those of you that claim you have run 100LL for years, I'm guessing you don't drive in cold climates as avgas makes for much harder starting in cold weather. It is also incompatible with legacy (old) seals an o rings.
Do you really want to know about fuel choices? Here is one of the best sites I've run across:
http://www.superchevy.com/how-to/car...-about-octane/