Talking about pronounced price difference between ethanol and gas, RON95 gasoline is 1.40€ a liter usually (slightly less since covid) and E85 is 0.60 a liter or less in my area.
Where does one rent a flex fuel vehicle in Europe? That would be a huge cost savings. I've always had diesels when I rented over there, but at half the price E85 would be worth a look.