I just looked, out of curiosity, and found this information on the amount of octane ethanol adds to E-10 pump gas. I still wouldn't make it as I have 91 octane E-free available 6 miles away if I wanted pump gas without ethanol in my high performance 2 strokes. I do use it in the mowers, generators, blowers and trimmers.
Looks like its roughly 2-4 octane points.
(Zachary J. Santner, senior specialist of quality with Sunoco, notes a few concerns regarding this process, with a very big one involving safety: Gasoline vapors are rather flammable and, thanks to having vapor density heavier than air, might collect unnoticed around your feet. One spark could then ruin your day/life.
Ethanol is added to fuel to increase its octane, so removing that ethanol yields a fuel that’s more susceptible to knock. In rough terms, this process would turn 87-octane fuel into 83, 93-octane into 91.)
Then there's this part of that process. Definitely wouldn't use it in my equipment or toys.
(Santner also notes that the phase separation used to pull the ethanol from gasoline is impacted by ambient temperature. “The colder the temperature, the better the phase separation will be,” he notes. But even under ideal conditions, he continues, this process could leave the fuel containing less than 1% water: “Any of that little dissolved water could lead to corrosion.” Santner also notes that the antioxidants added to gasoline to extend its shelf life are often water-soluble, so this homebrewed trick intended to create the perfect storage fuel could have the opposite effect by removing the additives designed to protect the fuel when sitting. )