FWIW, I've seen (across 7 cars) a 10% reduction in fuel economy for the gas with 10% alcohol.
Only in my camper was it a 20% reduction. 
This evening I confirmed, that with 10% alcohol gas, the fuel economy is only 11-12mpg, as opposed to 15-16mpg on pure gas. 

On Aug 30, 2013, at 4:06 PM, Timmy Evens <monkey_lips@YAHOO.COM> wrote:

> the btu's in a gallon of 10 % ethanol isn't much different than straight gas.  would not attribute to alcohol. maybe maybe bad O2 sensor?
> 
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> 
>