Most if not all Mogas today has Methanol in it as a replacement for
the oxygenation agent MTBE. Gas pumps are not typically labled as to
alcohol content. Both Petersen and EAA autogas STC's are not valid
with autofuels containing alcohol. At a recent IA seminar held by the
FAA we were reminded that even with an autogas STC if an airplane is
operated using a fuel containing any alcohol that the airplane would
be considered by them to be "unairworthy". Unairworthy to the FAA
also means uninsured to most aviation underwriters. So you won't have
a problem until you have a problem! Methanol is hydroscopic which
means it holds water. This water will, over time, rust the steel
parts in the fuel system.

Gary Plewa

On May 31, 6:42 am, Ron Natalie wrote:
Rip wrote:

Jim, sadly there is no mogas STC for the Navion, with any engine.

Rip

Yep, I even talked to Petersen about this (the EAA doesn't touch
6 cyls). All they knew was they had tested it and it had failed
the vapor lock test. They couldn't remember which engine, fuel
system, or model Navion they had used.