Its pretty simple, The water from the ethanol goes to the bottom of the tank, Ethanol will grab moisture from the atmosphere. E-85 is 85% ethanol and 15% gasoline.
Any Pump gas that DOES NOT say Ethanol-Free Can have up to 20% Ethanol in it, Especially the Premium Unleaded higher octane Fuels, Because they add ethanol to it to bring the octane levels higher. Pure Ethanol fuel has a very high octane of 114 octane. E-85 has 108 octane.
Super Unleaded 91, also known as E20, is a fuel that contains 20% ethanol and has an octane rating of 91
So people that tell you to get premium at the gas station and your carbs will be fine, Just simply don't know what they are talking about.