wrote in message ...

You can (almost) always run a gas that has a higher octane than
what your engine requires, so if you normally run 87 cargas (something
like 82 avgas rating), then flying somewhere that only has 100LL, you can
burn that without trouble.

Well the octane numbers aren't directly comparable. The major reason you
can run 100LL is because your aircraft was originally certificated for 80 or
100 octane Avgas. The STC doesn't undo the original certification, just adds
the option of of using autogas.