2000 Ford Excursion. Powerstroke 7.3L diesel 3/4 ton 4x4. 265 series 16inch tires. 3.73 rear end. Getting 13 to 14 right now combined mileage on winter fuel. On th eflat lands of Ohio with a/c off and cruise set to 65 (speed limit), I have seen over 20 mpg for mostly highway. Towing my 31' travel trailer, I get 9 to 10. My old '93 Suburban with 7.4/4l80E/4.10 got 5 to 7 pulling the same rig at 70 mph. You get much above the torque peak and diesels seem to start to really drink the fuel. They are real RPM sensitive.