The newer diesel Ford and Dodge pickup trucks use an extra shot of diesel fuel into the cylinders to provide the fuel for the regen process. This process causes unburned fuel to enter the crankcase oil thus the sooting problem This also affects the oil change interval. Recent models of the Duramax have an additional injector in the exhaust pipe for the regen whereby eliminating this sooting problem.
I have used POA formulated synthetic lubricates exclusively in everything I own that requires lubricating since 1986. I figure anything designed to run on petroleum lubes will run better and last longer with PAO synthetics. I may be wrong but the proof is in the pudding. As an example, my Harley has 90k miles on and it runs like new.
The value of synthetic transmission fluid and gear lubes is undeniable. Just ask Allison. In many high stress situations the same can be said for motor oils. Just my 2 cents.