RST Engineering wrote:

I do not quite understand why gasahol burns well in old Ford tractors that
use Marvel carburetors and is prohibited in aircraft with Marvel
carburetors, other than some bureaucrat with a bad comb-over deciding it is
so.

What I've read in a number of places is that there are problems with issues
similar to vapor lock in aircraft. Since gasahol doesn't seem to be causing
problems in cars that cross the Rockies, it seems to me that this wouldn't be a
proble for a pilot who rarely exceeds 10,000' ASL.

If vapor problems are actually the issue, perhaps an STC with altitude limits is
in order?

George Patterson
Give a person a fish and you feed him for a day; teach a person to
use the Internet and he won't bother you for weeks.