I've never really had any dealings with an mogas STC. Do they acctually do
anything to your engine or do they just change the stickers.

With most aircraft, it's a paperwork change -- period.

In some aircraft (some O-360 powered Cherokees, for example) you have to add
a supplemental fuel pump.

Both my Warrior and my Pathfinder came with the STC. In both cases, it was
a paperwork "upgrade"...
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"