wrote:

We used to do that with both O-320s and O-200s, and both gave
trouble on either straight mogas or the mix. Unleaded auto fuel is
significantly different from Avgas, and even getting the lead level up
to 0.5 ml/l with a 75/25 mix (to make it the same as 80 octane), we had
valve sticking problems. The O-200 was particularly troublesome.

My experience was the opposite. I had more trouble with 100LL than with Amoco
high-test.

George Patterson
We don't stop playing because we grow old. We grow old because we stop
playing.