I dont know everything. Trust me! I realize h9w much I dont know since hanging around my wifes kids shop. Lotta little stuff I had no clue about.
Three things i have learned.
6l have a bad rep that should be served on the behalf of the 6.4. A 6l with "the upgrades" is a 500k mile truck with normal diesel maintenance. Yean there are injector issues and the hpops do goofy shti too.
Secondly, the cummins isnt the danm best thing to happen to a pickup truck. The old 5.9 was a fine engine for a worktruck. 12v can make big #s. The 5.9 and 7.3 are the dinosaur work truck engines.
#3 is most people who "take good care" of stuff dont. Most people add fuel to the tank and keep hitting "reset" when the truck wants service. A big portion of the trucks we see have inadequate tire pressure, no washer fluid, blinkers not working, etc...there are some repaired that dont ever get test driven.
Did an obs with some 160/80s last week that didnt want the truck started after injector install because he didnt have the chip yet. He came and picked it up, started it with the chip and drove off.