Going from Regular Gasoline with 0% Ethanol to upto 10% Ethanol is the biggest drop I've heard from people. I think somebody even had a noticeable drop going from 5% to almost 10%. Some people swear they lose 25%-33% from E10
. I've never seen this phenomenon proven though.
But for anything E10-30 sometimes up to E50 people are reporting the same or similar MPG. This makes it more cost effective to run 30% Ethanol in areas where there is only 10% Ethanol in Regular and when the price drops enough on Ethanol people switch to E85. Although that was mostly the Ethanol guys, meaning those who actually ran high blends in their FFV/NonFFV cars, I hang out with on forums soo, YMMV. I know that there are several studies that correlate with this event. The Ricardo FFV V6 turbo engine had better balanced results with E30/40 aswell. And the DOE did a study on the most cost effective blends for modern cars and that was either E30 or E40.
And Toc, Ethanol is oxygenated. The burn characteristics of oxygenated fuels are significantly superior for energy efficiency compared to Gasoline. But the cost is energy density. It is not a simple equation of BTU = MPG for Ethanol. Eg. the typical MPG from E85 is closer to 75-85% of the mileage from E10. The newer FFVs are supposed to get even better, eg the new Regal.
I was recently made aware that the EPA MPG numbers for FFVs using E85 are total crap. They don't even test the cars on regular gasoline let alone E85. They just calculate the BTU per mile and adjust it accordingly. And the reasoning is because it is *illegal* to test cars on anything but octane
.
*Not going to discuss politics here.*
If you want a current number as of 2008 for the Energy return for Ethanol measuring just Fossil Fuel, the USDA has a current figure linked
here.
And PS unless they're mixing 85 octane with Ethanol the actual octane rating for Regular 87 octane with E10 is closer to 89 octane.