I know I'm getting into serious nerd territory here, but oh well...I've used E10 and it's readily available here in the Midwest since we grow most of the corn used to make it. There's an ethanol plant in Garnett, Kansas that I've been by before many times while driving. E10 is a little cheaper here, since the crops and the Ethanol plant are both relatively close. E85 is quite a bit cheaper, but has its drawbacks and can only be run in vehicles capable of using the fuel (Teg is not one).
Anyway, E10 typically has an octane rating of 2-3 points higher than regular straight gasoline. So the octane rating is typically 89, the same as our mid grade unleaded. We typically have 87,89 and 91 or 92 octane regular gas and (89 octane) E10 and (105 octane) E85. The E85 usually has a decrease in fuel economy by 20-30% due to less BTU potential in the fuel. Using some "fuzzy math" E10 has around 12% of the ethanol content of E85. This means that it would have approximately a 2.35-3.5% decrease in fuel economy in relation to regular 87 octane unleaded.
This calculates to 7-10.5 miles less, if driving 300 miles on a tank, or 293-289.5 miles instead of 300. These numbers are hardly anything to even complain about. With the increased octane and decreased price, I've even got better miles per gallon and cost per mile on E10 in comparison to regular 87 octane unleaded. So I don't agree that E10 alone is contributing to decreased fuel economy. Gas that's sold in the Winter, has been know to cause reduced fuel economy though, due to percentages of chemicals and additives allowing cars to run easier and smoother in colder temps. It's not Winter yet so who knows?
Last edited by mdb20; Oct 4, 2008 at 05:08 PM.