The 5.0 Cummins returned terrible fuel mileage which is why it was marketed in a "Heavy Half Ton" not quite a 2500 but heavier than a 1500 so fuel mileage did not have to be advertised. That motor suffered the same issues as our 3.0 VM's due to EPA exhaust requirements and incorrect driving habits for the regen. I agree the 3.0, even in the redesign, still needs highway miles, not rock crawling to keep the exhaust system happy so I see trouble ahead for that selection. My wife's 2015 Grand Cherokee delivers 27 mpg highway with her 3.0 and we have had no problems with the DPF that were not cleared up with a 20 minute drive at 65mph. She did manage to break the DEF injector off the DPF, I still haven't figured that one out, and the new injector required an Adaptive Relearn reset.
I have seen the Ford Powerstroke, Chevy Duramax, and the Cummins all fail due to clogged exhaust just like our little 3.0 VM, almost all due to incorrect driving requirements. When checking with my parts supplier the oil filter for our 1st, 2nd, and 3rd generations cost $16.50 but the 4th gen has a different part number and cost $46.00. I also have noted that
www.moparpowertrain.com now lists re-manufactured eco's on their website. Owner knowledge and dealer tech experience and knowledge, along with appropriate driving patterns go a long way toward a happy experience with this or any diesel.
My 2500 Cummins has exhibited a low of 14.7mpg and a high of 20.1mpg dependent on speed, head wind, towing, so for a nearly 8K lb. empty vehicle it is not bad.
The biggest challenge the internal combustion engine has at this time, diesel or gas, is the EPA and the Radical Environmentalists who populate it.