It looks like we're in similar situations.
I traded my '01 Dodge Ram for an '01 Expedition for my wife and took over her Ford Focus for my then long commute. Now I'm in snow country and the Focus doesn't cut it for daily commute.
So, I traded the '01 Expedition in for an '08 JK Unlimited X, 3.73s, 6 speed and gave the Focus back to my wife:innocent:.
The Expedition got the same mileage as yours.
The JK gets 20-21 mpg and the Focus gets 25-31 mpg!
The downside...my wife missed the Eddie Bauer cushiness and kids could buckle themselves in. I miss being able to slide a 4 x 8 sheet of plywood in the back and being able to tow 8,500 lbs.
The upside is that I'm commuting with sooo much more confidence in the snow and ice, can still build it like a Jeep should be, can fit the family in, have a better heater than the CJ... Just remember, even though it's a 4 door and it 5 inches wider than the TJs on the outside, it's not where near as roomy as your Expedition

. It's not really that much bigger than the Focus in the inside. I'm getting by, however, and I'm 6'4".