Sta-Bil will stabilize the fuel and keep the additives (mostly) in the car gas.

The problem is the car gas itself. There is so much unwanted BS added to car gas I don't like leaving it in the tanks to sit for long periods. Even the ethanol free variety has lots of BS in it. IMO, this is why older fiberglass fuel tanks have problems.

I would much rather drain and winterize with 100LL, a stable, fiberglass friendly fuel in it's own right. The LL will not hurt the engine. The car gas COULD hurt the tanks.