(R. Wubben) writes:

I'm trying to avoid ever having a stuck exhaust valve again, but the
reality is that 80 is hard to find and autogas is frequently not an
option (depending on the airport).

I flew my Aircoupe with a Continental C-90 from California to Oshkosh
last summer. At home I feed it 80/87 or mogas, but on the trip it got
100LL. It needed to be leaned more carefully, but otherwise ran OK.
As soon as I got home I started giving it unleaded gasoline again.
Quit worrying and start flying.