I can completely corroborate this with several vehicles. In the teeny tiny town where I am (no lake, no marina, no dock), they carry e00 (as "regular no eth"), e10 (as "regular"), and e15 in both super and premium. The E00 costs like $0.05 a gal more than E10. Absolutely nobody in this town buys E10, you can see em all line up for the one pump that has E00.
Running E00 in the company 2015 dodge dakota, the '90 ranger, everything but my GM (which has horrible mileage - think it needs the MAF replaced). I got a full 30% better MPG on the dakota, tank after tank after tank. Whenever I am forced to go back to the big city (Denver/ whole front range metro) where there is no E00, I get crappy mileage coming back.
I can't testify about the other family vehicles, but they all run E00 90% of the time as well - complaints that it runs like crap and "go through a tank incredibly quick" on anything else (which I interpret as bad MPG).
full vehicle list:
'18 escape
'15 dakota
'07 ranger
'07 pontiac G6 convertible
'06 pontiac G6 convertible
'90 ranger
.....something Chevy 2500 pickup, don't know, mom's boyfriend not interested in asking specifics (probably roughly a '00).