had ethanol w/stabil go bad in my chevy II that I foolishly let sit nearly 2 years. had to clean out the brand new gas tank with lacquer thinner, all the rubber lines were swollen and turned into a funky soft gunk. Haven't fired it up yet (have to order new plug wires as I installed different distributor) to see if I have to change fuel pump/rebuild carb. My LTD sat maybe 6 months without moving, it ate up new fuel pump and carb. It attacks rubber if it sits. My mower was running rough, checked fuel lines, they had swollen and soft/gummy. I noticed a new Holley I bought had a tag metal wired to it that said use of any ethanol gas voids any/all warranty.
I don't go to the trouble of hunting ethanol free, but I try to keep things moving more frequently now. I think if moving regularly (maybe weekly), it shouldn't cause issues, seems to be when it sits.
about the zinc, I asked a local machine shop, they felt if your motor had ever been ran with zinc and broken in, it could safely be ran later without any additive. They said same about lead, if it had ever been ran on leaded gas, the valves were coated and likely unhardened valve seats would last decades in the weekend driver.
