Another boring mpg story…
It's dependent on use, storage, & how well the system is sealed when dormant. I have over a dozen vehicles, a lot of them outdoors. If You're not running a full tank thru' them once or twice a year, it turns to ****, I've already posted what happened to My "71 Olds, My '88 ShelbyZ, etc. elsewhere before, I've always kept the fuel full as possible in the tanks & ran them/topped 'em off every year at least twice. Going from current conditions, then having the temps drop dramatically, causes humid air to be pulled in just to condensate inside the tank.....which in turn is attracted to the alcohol in the fuel better than the gasoline.
None of My daily or routine drivers, carbed or otherwise are affected, now I use Stabil360 in everything that sits..so far so good. The other plus is, being near the Mon. River & a large Creek w/multiple Marinas, alky-free 88octane is now easy to obtain with more large chain convienience stations popping up in recent years.