Jay Honeck wrote:
The PA-32-260 engine variant (E4B5 or whatever) is in Petersen's list as
one of the 91
octane engines. However, the airframe isn't approved.


That sucks. Guess I'll never buy a Six.

How does an airframe difference matter to what fuel the engine uses?

Fuel lines, fuel pumps, and vapor lock issues. Lots of information on this
on the Petersen web pages if you want the details. They don't do Navions
(with any sort of engine). I asked for details once and the emailed me back
that they had tested it and it failed the vapor lock tests. I asked for
further configuration information because even with the E-185 (original Navion
engine) there were two different fuel configurations (that's the difference
between the Navion and Navion A), and then there are other engines (also on the
approved list) that the factory and/or outsiders have added.