I've got a few customers at work with 2500 4x4 CTD getting 18-20 mpg highway unloaded (new/def system). The oil change interval is nearly twice what the early 6.7's were (if you go by the minder). Fuel filter cost doubled (two filters now which were needed years ago....same 15k interval pretty much).

I've worked on a couple of the new 6.4 2500 4x4's. Noted the average mpg on one was 14.6 and the other 16.2....overall not too bad for a gas truck of this size. Would sure love to know how it pulls.... if we get one in on trade I may have to test that theory with my trailer. I'd honestly consider going this route.