My plans to track mileage on the interstate was marred by construction delays, traffic stops and rain delays but here's what I learned, 180 miles at 75 to 88 MPH, 15.9 MPG. 40 miles at 74, 17.0 MPG. 65ish miles on highway, 68 MPH, 17.9 MPG. Mixed travel, 70 miles interstate/turnpike at 77 to 85 followed by 35 miles of through towns highway driving at 30 to 65 MPH with frequent stops, 16.2 MPG. Overall, based on previous identical trips made in my 04 2wd Titan, my Pro4X XD gets the same mileage as my old Titan, but rides OH SO MUCH NICER!!! The guy that rode with me is a die hard GM fan. He was actuall involved with the R&D for the DuraMax project when GM started that. He made the comment during the ride that the XD may make him switch brands.
Also, I got to use the 4x4 this weekend, worked flawlessly, and effortlessly. Front end had fallen into a washout on field edge, unable to blackout in 2wd, placed in 4 hi, eased on gas, no clunk, no jerk, just smooth lift of the front end up and out of ditch.