Jon, we really appreciate you looking into the diaphragm material.
Kevin, from what I read in an EPA letter, about leaving a can of E10 open to air for 200 days, the Ethanol in the gasoline binds with water (air moisture). The mixture is heavier and separates to the bottom of the tank (or gas can or container). The gasoline above gradually becomes Ethanol depleted. All this depends on time, humidity and temperature. I've seen extended length tests where the Ethanol-water mixture will eventually separate to mostly water on the bottom and a cloudy mixture layer above. The Ethanol depleted gasoline still resides on top. To give some kind of answer to Mr. Panic, since the Ethanol is still somewhat diluted, I would guess it is less corrosive.
