Just thought I would throw this in. We just completed a 2300 mile trip from Silver City, NM to South Padre Island, TX and back in our Commander. Gas milage broke out about like this:
TX roads traveling at night speed limit is 65 mph, kept it at 68 mph for about 500 miles and got 21.2 MPG
TX road traveling during daylight on return trip, speed limit is 80 mph and kept it at 80 for the 500 miles and got 17.6 MPG
Overall, I spent $353.00 in fuel, 117 gallons of fuel, average $3.00 gallon, Lowest paid was 2.79 and highest was 3.19. Figure somewhere in the 19 mpg range for the whole trip.
Commander now has a little over 10,000 miles on it, have the 4.7 V8. We loved it for the trip, it was comfortable, fit the five of us very well. With the exception of having to replace the left front tire to the tune of $198.00 due to a rapid deflation after running over something at 70 mph, it performed flawlessly.
Note, when tire deflated, the Commander never swerved, or lost control in anyway, this was not a blowout, but a very fast deflation. I was impressed with how the Commander and the tire held out.
Last note, didn't buy it for the gas milage, just kept track for fun, we love our Commander