As long as it's Top Tier Fuel, I doubt you'd notice any difference in actual MPG. There are a lot of other variables that would affect MPG from tank to tank, such as outside temperature, tailwind or headwind, over/under inflation of tires, amount of extra weight in the car, stop and go city driving vs freeway driving etc..
Because of the different ways different refineries mix their gas batches, and differences in particular local distribution systems about which brands get which refinery outputs -- or even swap commodity base stocks among them -- any "best mpg" results in one area likely don't carry over to other areas. Or even season to season.
Lately seeing a push around here to brand E15 fuel as... well, anything other than E15. Any car will get reduced MPG on that stuff due to reduced energy content of that fuel type. When the consumer doesn't understand that it isn't the same as regular gasoline, things get confusing.
Are you just getting E15, or always had it. None here, but did try it in the Camry when down south. Sheetz was pointing out it being higher octane; close to midgrade. Likely of no import to the Camry, but I figured the lower price more than made up for the lower energy content.
Mostly noticing that Sheetz is going out of their way to advertise it as "Sheetz 88." They're not hiding the fact that it's E15, but they just seemed louder than usual in branding it as, well anything other than E15. I haven't knowingly tried their E15 in our Prius, but there aren't a lot of their stations on our common routes.
That's how I remember their signage in NC and Va when I had the Camry. I only tried it because of the lower price at those locations. Subaru says no to E15 in non-turbo engines, so haven't driven past a Sheetz since then.
No unless it's not Top Tier. (Got poor mileage on a tank once in middle-of-nowhere Saskatchewan). Also, if it's E10 vs. non-blended fuel - that will make a difference but given that now practically all 87 grade fuel is E10, there's no longer the option around me for non ethanol fuel.
Reduced engine lifespan too. This is due to laminates building up primarily and less so with issues with Ethanol having the nasty habit of absorbing water. The whole dishonest racket was entirely for the corn industry to expand their sales numbers by ensuring that legislators believed the lie that adding ethanol would make cars burn cleaner without accounting for the fact that production of Ethanol actually leads to much greater amounts of air pollution / greenhouse gases, not less.
