 I have 40,000 mi. on my 2012 4.6L 385hp v8 sedan. With(10% ethanol) premium gasoline 93 octane, I get 21mpg around town and 26mpg on the highway in cruise (65mph)  I found a gas station in NH that sells pure 91 octane gasoline (no ethanol) I fill up there often. My gas mileage immediately goes up to 31mpg (in summer) in cruise control at 65mph.
Try to find a car anywhere that has that much HP and still gets 31mpg.  Incredible ! (shows what a scam ethanol is also)