Since boats are stored almost every season, the National Marine Manufacturing Association ( NMMA ) tested many different marine tanks, with ethanol mix stored for several months. Their findings: Separation can occur if the tank is not tightly sealed. Yes, the gas-ethanol mixture is much more corrosive than just gasoline. Car tanks have been hugely upgraded (plastics, triple nickel plating, etc) to deal with this issue, but if you have a choice.....
As you probably have read, the ethanol will only separate out if the percentage of water gets to high (Ethanol slowly absorbs water from the atmosphere) then it separates out all at once.
Our local corner BP station had this problem last winter, quite a lot of cars were disabled after filling with ethanol,- including a brand new Toyota that was returned to the dealer for "warranty service". After many customers complained, ( several cars only went a block or two, then stalled) it hit the evening news and BP finally admitted the problem and agreed to fix the cars. Then, claims between the station, the tank truck and the pipeline........... all pointing fingers at each other.......
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