Ruin paper element fuel filters? I ran it all the time in my 68 cuda with a see through paper element and have never had a fuel system related problem. Never saw it "clean all the rust out of the tank" or even had 40 year old rubber line give me an issue. I think a lot of guys have issues they just want to blame on the ethanol. It is actually a preservative and not corrosive, you can drink straight ethanol and live to tell.