Hi Allan,
I use the Wynns Gold Diesel treatment (from Halfrauds), I add it roughly every 4 fills, I use Shell V Power and have never had and DPF or EGR issues in 40'000 miles, my car purrs smoothly and cleanly.
Just my 2 penneth.
Dom
not necessarily, i used to have an s-type with engine light on periodically. It was the DPF and after using millers it kept the light off. We used the same stuff to maintain octane when we drove our Navara to mongolia. If you fill up with diesel in mongolia the engine sounds like a bag of spanners
Yes there is a lot of snake oil around but some stuff works.