Dana M. Hague d(dash)m(dash)hague(at)comcast(dot)net wrote in
:

Back in the 1980's when I still had my 1941 T-Craft (which had an A-65
and ran fine on the leaded regular mogas which was still available at
a few stations then), I looked at the type certificate and all it said
was "73 octane minimum". Never was clear whether that meant mogas was
legal even without an STC.


Well, kinda. Avgas was only relatively new when tha airplane was made. Most
antiquers today shy away from avgas if at all possible (I'm talking about
guys running early Wrights and Kinners and so on now) My LeBlond specifies
a minimum of 60 octane, which is basically carrot juice and doesn't like
lead at all..There was an Avgas, before my time, that was a levle below 80.
90 was still available, though scare, when I started and I have seen
115/145 not all that long ago in places that DC7s and what not were still
frequenting and any place the US Navy was still operating P-2 s in earnest
like Keflavik.
IIRC the 115/145 was purple, the 90/98 was blue and the 70ish octane stuff
was brownish yellow, but never having seen it I only knew that from
whatever books or lists still carried that info.
But the little pre-war designed flat fours were widely run on mogas after
80 started getting scarce, STC or no STC. The FAA doesn't seem to be too
bothered about it.



Bertie