I would think your little V-8 Expedition should be able to do better than that 13 MPG tank, my V-10 Excursion 4X4, 4" lift with 4.88 gears can give me 14 MPG highway and about 11 to 12 around town using a few of the hypermiling techniques found on this site, nothing crazy just a lot of coasting and close watch on the Ultra-Gauge. Before I swapped to the deeper gears I had 3.73 gears from the factory and could get 15.5 MPG highway with a full load (8) of adults on board. Earlier this year I was able to average 9.0 MPG comming from Savannah GA to Philly with 5 adults and gear while pulling our high profile 9500lb ToyHauler camper. Kept speeds between 63 and 65 MPH and worked the throttle to keep the trans in OD all the way.
I know 9 MPG is a pretty low figure to be bragging about on this site but considering the vehicle, load (18,250lb CGVW) and aero I'm pretty happy with it. Prior runs along the same route with the same load and the factory 3.73 gears were about 7.25 MPG.
