Does E10 (10% ethanol blend) have a winter mix?

[RU482]

I have an 04 Impala w/3.4L
I don't see much of a mileage hit from using E10, and it's cheaper than regular unleaded, so I use it. Over the last two weeks, my mileage went from ~24MPG to ~27MPG. I fill up about once every 5 days.

I did not change anything on the car, nor my driving style. THe temperature has also been about the same.

I know that regular unleaded has a winter and summer mix, but does E10 also have a different winter formulation?

Oh, I am in the midwest, if that makes a difference.

 

[nakedfrog]

MTBE, maybe?
I'm in the midwest and every car I've ever tried E10 in has consistently shown 10% less MPG.

 

[luckysnafu]

Yes, the other 90% of the volume is regular gasoline, which has a winter blend and a summer blend. You are getting better mileage since you are running the summer blend now. My mileage recently went up as well.

nakedfrog: I am pretty sure that MBTE has been outlawed in most (if not all) states now. Every gas station I go to now has a sticker saying minimum 10% ethanol by volume.

 

[potato28]

They add something to E10, Petro Can's around here switched from their winter blend back to the regular mix that usually gives you better gas mileage.