2015 2500 4x4 regular cab long just turned 157K on it with only issues being carrier bearings in the rear at 150K. I tow 11K lbs, just went to Carlisle and back 1700 miles all told. It is just adequate over the mountains, some 5% passes got down to 35 mph, so I wouldn't do it a lot. Averaged 7.2 mpg at a 62 mph average. That is of course over lots of mountains and headwinds coming home, got 8 mpg with tail winds going east. It is a bit of a rough ride unloaded and a real buckboard on Illinois roads, you know all about that! I didn't want the 6.4 due to the MDS because I do tow at least 50% of the time and didn't need anything extra that would break, most of you know my record with transmissions, and so far this one had been fine. I love the truck, and it works for what I want...