Don't get topics confused ...
As I understand it, the DPF is required because it treats the exhaust particulate (hence the name of the equipment). This is specific to the regeneration cycles needed at times, to heat the PDF unit so it will burn off the soot. The raw fuel is injected in one of two ways. Most common is the "in cylinder" approach where the fuel is shot into the exhaust cycle, and pushed down to the DPF unit to be burned. This is the more common approach. However, GM (Dmax LML) just introduced a 9th injector in the exhaust piping downstream of the engine; hence no fuel/oil dilution. Costs more to have a 9th injector, but it certainly solves oil contamination issues.
The use of urea (SCR - selective catalyst reduction) is used to threat the exhaust gaseous emmisions, specifically nitrogen oxides IIRC. EGR can also be used to treat nitrogen oxides. The Ram truck uses EGR rather than SCR as a matter of chosen bias against less regular maintenance costs, etc. Urea costs money, and it's perceived by some to be an inconvenience in regard to maintenance fill ups, etc. OTOH, the heavy use of EGR has other undesirable effects such as heavy soot loading of the oil and EGR system components. In short, it's a "choice" that the Ram truck folks made; they prefer the EGR over the SCR.
It's important to note that, in regard to DPF and regens, the more you work your truck hard, the less regen events take place. Guys that tow hard/heavy all the time actually have less regens and less EGR/DPF soot contamination because the system gets really hot (desirable) from normal use. OTOH, guys that use their trucks to make a run to Home Depot for wood for the back porch deck, and drive the other 99% of the time to work and back while communting, see a lot of DPF loading and therefore a lot of regen events. These guys often complain about the costs of operating a HD truck; the regens, the EGR cleanings, the cost of urea, and it's their driving cycle that is the root cause. They don't "need" a diesel truck; they "want" one. And they pay a heavy price for that in higher maintenance costs and equipment issues. They can "delete" exhaust equipment and "alter" engine programming, but eventually it will catch up to them with exhaust laws. More and more states are now testing diesel trucks along with cars for exhaust emmisions. "Lost kitty" and "DPF fell off" approaches are short term fixes for long term issues. I fully understand that those fixes work; but they will eventually be made unavailable as the "tree police" get ever more vigilent.
I'm not saying I have a preference; I see the benefits and limitations to each approach. I'm just trying to clear up the concept of DPF, SCR and EGR use.
If I got the terminology wrong, feel free to correct me. Just going by memory here.
