What would actually happen if you put normal car petrol into the tank, for an IO-540-C4 for example?
That's a good question. An acquaintance of mine flies mogas in his IO360 DA40F. (covered by a mogas STC) But I'd personally be wary of doing this on a IO540.
Any old twin worth it's salt is going to guzzle 25-30gph Avgas
Should not be as much.
I'm not sure why, but I generally hear even higher consumption figures quoted for these old twin guzzlers. A friend of mine flies a C340, and it's running ~35gph at 75%. Try that with non-US avgas prices, and you're talking serious cash for even trivial trips. Although as people have mentioned in this thread, what's really killing the old twins are the damn maintenance bills.
I've shelled out $35K this year alone in maintenance (bless her heart).
Adam, please tell us it's been worth it after all!
