Does the Ford Excursion diesel really get 18 mpg?

I'm thinking about getting a Ford Excursion Powerstroke diesel. I read somewhere that they can get up to 18 mpg city. Is this really true?

Added (1). I forgot about fuel economy factors such as driving habits and weather. Can it really get mid-upper teens in the city?

Added (2). I forgot 4WD.

We got 16.7 MPG highway at 70-75 MPH with a 7.3L diesel Excursion on a 400 mile trip (each way). Which is quite good considering the size of the vehicle. But you aren't going to see 18 MPG city in an Excursion, around town you might get 12 MPG.

What is with your constant questions about fuel economy and large SUVs? In case you haven't figured it out yet. Good fuel economy and large SUVs are mutually exclusive, you can have one or the other, but not both.

NOPE! Try 12-13 city and MAYBE 18 highway