I’m not so sure this is true. Mogas with 10% and above ETOH is certainly unstable. Shelf life of alcohol laced fuel, is similar to that of an alcohol laced pilot…very very short, less than a month or so. It’s worse when stored in airplanes. gaskets expand, fuel hoses leak, water/etoh extraction corrodes. Not a pretty picture at all.
ETOH free mogas has a shelf life of about 6 months to 18 months under appropriate storage conditions. It’s not clear how fuel leads to a crankshaft failure as there should not be much fuel in the crank case, and what is there should be evaporated off as soon as the oil comes up to temperature. More likely, the load on the crank shaft and duty cycle on those engines are the culprits. I don’t think I’d put an automotive engine in my airplane either.
Avgas is usually stable under appropriate storage conditions for about a year, so there isn’t much difference between ETOH free fuel of one or the other stocks.
As for storage, I believe Cessna has three levels of storage for a/c, flyable, temporary, and long term. Short term is pretty standard, fill the tanks, turn off the switches, tie it down, Fly it for half an hour every 30 days. Amazingly the CSL says if you can’t fly it ground run it for 30 minutes…now I know where that old saying came from…not recommended these days, I think. For long storage, take the plugs out, spray the cyls with anti-corrosion stuff and put the plugs back. Fog the engine compartment through the oil filler, put desicators in the plug holes, exhaust and breather and tape things shut.
None of these procedures suggest draining the fuel out of the airplanes for the winter. This was written before the hairbrained idea of putting ETOH in fuel came about, so if there’s alcohol in the fuel I’d drain it. I use ETOH free mogas in my farm equipment and it makes the winter just fine with similar preservatives.