Bruce
I've used mogas for so many years I've forgotten when I started. Use
the supreme and you should have no problems. I don't know the tech
reasons or the difference in heat generated on the valves, but as a
precautionary measure, I kept the mixture just a little on the rich
side for power applications. Never had a single problem that could be
attributed to the use of mogas. Used it in both low horsepower, and up
to the 300hp in ag aircraft.
I HAVE heard of guys who tried to go the cheap gas route and had
premature engine failures or overhauls with valve problems. In the long
run they ended up paying a lot more for their pecuniary efforts.