I see I'm late but I'll chime in anyways. I have a 2007 3500 megacab SRW 4x4 with the 6.7 and 6sd auto trans. I have 310,000 miles on it. The usual brakes, tires and u-joints. The front end has been rebuilt once at 175,000 (ball joints, steering linkage and hub bearings). Oil changed every 5000 miles, trans flushed every 50,000 miles. Yes, all the emissions are deleted. Like others have said, 10mpg when loaded heavy, 12-14 mpg when loaded light and 18mpg empty driven daily. I have made several trips empty with the cruise set at 60 mph and have seen 22-24 mpg. I love my truck and plan on taking it to a million.
Casey in SD