If it has any effect it will be very minimal. Here's a validating quote:

"Allen Davenport, with Ranken Tech, confers that "you will loose very little power or gas mileage using E-10 fuel. The average loss of gas mileage with E-10 is about 2% and the power loss is not noticeable. The BTU (heat units) per gallon are very close between E-10 and straight gasoline, I seem to recall about 4,000 BTU per gallon difference which amounts to about 3%, however because of the better burn of the ethanol you gain back about 1% in efficiency".

The upside on the use of ethanol blended gasoline is as follows:

"Gary Whitten, Ph.D., principal of Smog Reyes, a California-based firm that provides air-quality consulting and research, recently found that gasoline containing 10 percent ethanol: Reduces carbon monoxide emissions by up to 30 percent. Reduces fine particulate matter emissions by 50 percent. Such emissions pose a health threat to children, senior citizens and those with respiratory ailments. Reduces emissions of smog-forming volatile organic compounds by 12 percent. In addition, Argonne National Laboratory, a U.S. Department of Energy laboratory operated by the University of Chicago, found that gas with 10 percent ethanol produced a 12 percent to 19 percent reduction in greenhouse gas emissions linked to global warming."

So generally speaking, using 10% ethanol blend apperas to be more positive than negative for most drivers that can fillup at the gas stations that offer the blend.

I've been using ethanol blended gas exclusively for the last 4 years specifically for the reasons outlined above - and I do not regret it.

Regards;

MS