That's exactly what I did. Ordered a 2x4 SV diesel with upgrades in the beginning. Read issues w/ early releases, truly evaluated needs, (cause I wanted a diesel, BAD) and decided to go gas, I stepped up to a gas Pro4X w/ utility package, (which the RockFord Fosgate system is worth the money alone,) for LESS money.
My daily trip consists of a 12 mile trip through town, round trip to work and back, and any other short trip I may do, I'm averaging 13 MPG. Have been on Interstate a couple times at 75 - 80 MPH, showed 16 to 19 on computer. Have noticed as high as 22 when running 60 ish.
Have pulled my boat, 2200 lbs. hardly noticed load, not much difference in mileage. Pulled travel trailer, 4500 lbs. with 1000 lb. golf cart in bed, for a short test run, without weight distribution hitch, truck sat down about an inch and a half or two, at or just below level. Truck had plenty of power, very stable and confident, didn't track mileage as trip was only about 10 miles with stops and goes.
Will get it on the road with a trip to GA the end of the month, then I'll report what I get on that trip, approx. 750 miles.
I think I've said it before, but, I love my truck!!
My 04 Titan 2x4 does 13 in town, 17.5 on interstate at 80 mph. It towed the same travel trailer getting 6.5 mpg with a 15 mph headwind, or 8-9 mpg normal conditions, at 60 - 65 mph. There is zero comparison between the XD and the 04 as far as stability, squat, power and ride with same travel trailer, plus extra 1000 lbs. in bed of XD. I would agree that 10 to 13 mpg while towing at 65 - 70 mph will probably be close. I'll find out this fall when I hook up and start camping.