We've had ethanol in our gas around here for a number of years...Biggest problem I've encountered is with my John Deere tractors (1996 & 2001 model yrs). Used to get carbon deposits that would stick the valve in the guide - then start up after sitting and...DOINK! Push rod would fall over due to stuck valve.

Fresh gas - clean filters. Didn't matter 1 hour or 1 week between starts.

1st attempt to remedy: new head, and JD update with new cam gear (eliminate nylon gear) stronger valve springs. 1st time out after 15 hrs labor and $600 in parts...DOINK! Same thing. Put back together, double check lash...DOINK, DOINK, DOINK!

Final fix: Sea Foam in oil and gas. Skip one or the other...DOINK!

Never a believer in sea foam until this happened.