For the past 3 days, I have been buying 87-mid grade which has zero ethanol. At a new Maverick station at Chambers and I-70 in Aurora, Colorado. My gas mileage has increased by 2 miles per gallon. Of course that gas station also sells gas with ethanol. The customers get a choice.
years ago, I had a Honda Prelude and drove almost exclusively on the interstates at 70 mph +- with cruise control
Gas with ethanol always yielded 3 mpg lower mileage
There is a website called Pure Gas that lists stations all over the US that sell real gas. They also have an app. It could use some improvement, but it’s still helpful when traveling.