14 newer 4x4 Cummins 3.4 gear..... 20 mpg pretty common. Deleted or not. Just an observation from work.

Injector failure common? I’d put that in the “not really” department. My only injector concerns are pumps and injectors on old junk like my 01 that was designed “pre” ulsd. For that I add a little 2 cycle oil, especially towing in the hot summer months. I do agree that the “tolerances” that these newer injectors use is on the stupid side.... these are work vehicles, not lab rats!

Def issues.... few and far between. Think I’ve replaced 3 def pumps ($$$), few SCR catalysts here and there ($$$)

Were old diesels better? Yes and no.... the ease and simplicity of an old P pumped 12 valve made for a great cheap reliable sub powered vehicle. Sure it’d get the job done, just don’t be in a hurry. The newer ones (14+) you can enjoy 900lbft torque and get pretty good mpg with the right combo.... (read: NOT a 4.10 geared 4x4 dually!)