Unless you're really digging for info about ethanol fuel, you are not really likely to find much where it matters IE: behind the wheel.

Ethanol does serve as a 'volume expander' for gasoline and it does increase octane ratings (lowers the likelihood of pre-ignition under compression.) Since etOH actually has a higher, 116, octane rating (depending on how it's tested.)

BUT, when mixed with gasoline and burned in a car engine tuned to burn gas, it lowers the BTU (overall heat generating capacity) of the given volume it's mixed in. The change in mileage can be accounted for somewhere, even though one might expect it to be the reverse.

CAVEAT: What any of us buy at any given gas station one day might not be the same the next day. Regardless if we buy at the same time, from the same pump. The pipeline/transport system carries all kinds of stuff and what comes out is seldom if ever identical over time.

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!