I could definently believe 505 if you were travelling at an economical speed without the airconditioner on and the windows closed.
Figure if I got 400 with 11 gallons, that's almost 40MPG. The light doesn't come on for 2 more gallons, that's 480 miles. And I was travelling at 90MPH with the aircon on.
Somewhere around 80MPH seems to be the magic number for fuel efficiency in my limited experience, at least for my car and purportedly a number of others with Zetecs/ATX too. Much higher than normal cars.
