In my area we are blessed with 15% ethanol  in the winter months.  My Chrysler Minivan drops 3 1/2 to 4 mpg vs the 10% ethanol and summer temperatures.

John - "The Hoosier Hurricane"

H H, is that 15% across the board, like, premium fuel also?  If premium becomes 15% ethanol too, I have a suspission many of us will be doing a little carb tuning. In another area above, Ted posted  BTU numbers putting this in perspective.   My '22 Ford Ranger lost an additional 1.5 to 2 mpg this winter but I haven't tested the fuel lately for enhanol content. 

64F100 57FAIRLANE500

I don't know if the premium is 15%.  The local papers only noted that the Indiana legislation approved the 15% gas for the state, and the oil companies jumped right on that.  Happened last year.  I haven't tested for alcohol..  I realize that some of my MPG loss is related to winter driving coonditions.

John - "The Hoosier Hurricane"

If burning premium (like me) to avoid excess ethanol (though a stock 292 should run fine on regular), likely one compensation some are missing might be increased initial spark advance (?). Could thus even gain back a few mpg (?)

6 VOLTS/POS. GRD. NW INDIANA

I remembered, after my last post, what my local Marathon guy told me, (before the 15% winter fuel) that he could get 90 octane non alcohol gas for me.  He said it was premium gas without alcohol, and if the alcohol was added it was rated 93 octane.and sold in the local gas stations.  So we were  getting alcohol  in our premium gas,  but I don't know how much.

John - "The Hoosier Hurricane"

Using 113 for the octane of ethanol, then a 93 octane gasoline with ethanol calculates to be an 8.8% ethanol content.  The summer blend for premium in my area is 3-5% ethanol.  Not sure if there is a winter blend in my part of the country.

Lorena, Texas (South of Waco)