Hard to say.... I drove a 600 mile per week commute and was happy when I got 600 miles per tank. To expect more than that, you'd have to be in a tail wind, driving downhill, both, or not measure things right.

The 45 mpg tank was a fluke. If MB left that much for mpg on the table, then shame on them. These cars get 30mpg with the hammer down on the highway, 33 with a light foot, and maybe little better if conditions are perfect. Anything better, you just didn't measure right.