Question on using Ethanol free gas?

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Hi everyone, I have an option of buying a mid-grade ethanol free gas, should I run this in the bike, I should get better gas mileage, and it's better for the rubber, etc, hoses and such, are there any drawbacks, I know it say's to run normal cheaper less octane gas, I don't remember the octane in the mid-grade, but it works well in the 66 mustang!