I've tried running E0 87 in my truck for a few consecutive tank fulls and only saw small mileage gains, not enough to offset the extra price over E10.
Fifteen years(?) ago, I did as you did & also saw little monetary gain in using E0. Later, with accurate past records of E10 use(not burned efficiently in low 87 octane, low compression ratio gasoline engines), I repeated tests, only with hundreds of tanks & year-round burnings of efficient E0. Now I have records for my 5 low 87 octane, low compression ratio(9:1 to 11:1) gasoline engines, registering 8%, 8%, 7%-8%, 7%, & 5% mpg losses with E10 as compared to E0. Yeah, E10 is still cheaper, even considering E0 superior mpg. But, EPA & "ethanol in gasoline industry" have worked hard to dilute our national gasoline stocks with E10 & make E0 rare, thus increasing its price. If E0 WAS available at 300,000 stations, E0 would be cheaper, miles per dollar, than E10.
The auto industry, drivers, & america have laid down, while "ethanol in gasoline industry" steals your money & doesn't give an effective fuel.
I see about a 2 MPG increase on my truck. That does not sound like much, but it is over a 10% increase.
Low mpg vehicles, raising mpg by 10%, will save a lot more fuel over the same distance, than already high mpg vehicle drivers, raising mpg by 10%. For every 110 miles traveled by a 10mpg vehicle raising its mpg by 10%, 1 gallon is saved. However, only for every 440 miles traveled by a 40mpg vehicle raising its mpg by 10%, will 1 gallon be saved.