So does the EPA, itself, who rates gasoline-engined vehicles for mpg, testing with the equivalent of 100% pure gasoline. Gasoline engine vehicle manufacturers love that EPA ratings with 100% gasoline, because the EPA gets the highest ratings with 100% gasoline.
Thousands of drivers using 100% gasoline get higher mpg, some even beyond 10% better. My earlier 3 cars gained 8%, 7% & 5% better mpg after switching to 100% gasoline from 10% ethanol blends. Presently, my 2013 Hyundai Elantra (yes, I even bought it AFTER the EPA downrated its mpg ratings), is averaging 38.9mpg, with a high of 43mpg, which I think, I can get higher.
All my car engines run smoother, quieter, & with a bit extra low rpm torque, such that less down shifting is needed for ascending hills. Ran on a segment of the experimental quiet pavement with Elantra. Suddenly, Elantra was like a quiet magic carpet, with little road, tire & wind noise....... & no engine noise.
Drivers using 100% gasoline support the 6900 stations, now selling 100% gasoline, up from less than 4000 stations, 3 or 4 years ago.