You don't need to believe me, test it yourself.
Go find a stretch of highway where you can drive at least 10 miles unimpeded without climbing into the Rockies, set your cruise at 65, and reset your tripometer. No AC, windows up, no defrost (see the no AC comment).
Report back the number your display shows you for average MPG after the 10 miles.
It will overestimate slightly, but do you want to bet that it shows mid 30's or above for the 10 mile test?
Granted I did this test in the summer with temps about 75 and regular blend gasoline, but I was showing 36+ mpg in my car (rated 33mpg highway) during my 10 mile test, this was a test that I repeated several times.