If you get a big Jeep, get the hemi, or at least a V8.
I have a Liberty, does ok, but pulling a bike trailer, my milage drops from 20-25 to 10-12 mpg. At worst, going uphill in the Rockies, 7-8 mpg, at best 15-17 on level ground (like Nebraska or Kansas)... But my little Jeepie weighs 2 tons stock anyway.
My next whatevers is going to have some real pulling power!
And 4WD!
Mary