You need an STC. I have the EAA one. Just go to their web page. You
can actually burn 87 octone fine on your O200 just make sure it does not
have ethanol in it. Cessna Pilots Associate actually recommends a
mixture of 100LL and AvGas for O200 and O300 engines after break in as
it better approximates the 80 Octane these engines were designed for
that the 100LL you are probably using. It will reduce your fowling
problems and stuck valves, and you won't need to run MMO.

Helen

Dallas wrote:
My C150M POH shows an approved fuel grade includes AVGAS 80.

Assuming you could find 80, how safe is it to run?

And, what are the modifications made to the fuel system to run MOGAS?

On a purely theoretical level, what would be the ramifications of fueling
up an unmodified Cessna 150 with 92 octane MOGAS?