I don't rely on the computer's calcualtor for mileage since the averages get watered down over time, and it calculates remaining miles based on past driving habits. Basically, we went from our house to Dayton, OH (188 miles). We filled up before we left and by the time we got to Dayton it was at 3/4 tank. Since the tank is listed as 17.5 gal, 1/4 tank is 4.375 gallons. 188/4.375 is 42.971 mpg. So, actually, I listed it wrong. I've noticed w/ all four windows down, the mileage is best. Next is windows up, air on. Worst is just the front windows being down; must be too much drag on the car. There's a lot of buffeting w/ just the front windows down anyway, and that's annoying.
I've also got 8,000 miles on the car, so that may factor in also. I use Castrol Syntec 5w20 w/ a Fram ToughGard TG2 filter (same size as my 94 V8 T-Bird, and the Crown Vic HPP and Mustang GT I had in the past). I thought that was pretty cool.
I wish Ford would communicate with owners like ourseleves and use that as testimony. I'm greatly impressed with this car and get compliments on it all the time. That, combined with comfort, quickness and mileage makes for one heck of a nice car!