Diesel engines are oil burners. Don't let the fact that the car and the engine are fairly new allow you to lose sight of that fact. Diesel fuel is oil, very much the same as heating oil, and your engine burns it. The exhaust will get black and sooty and there's nothing you can do to prevent it other than to stop using it. The DPF stores particulate matter when driving at slower speeds, ie around town, and regenerates to clear the DPF when driving conditions are more favourable. So DPF or not your exhaust will still get sooty. The DPF doesn't solve the emission problem. It merely allows for the problem to be moved to a place where the harmful effects of diesel combustion are less critical.

Edited by Railroad. on 01/11/2016 at 13:21

I suspect the sooty tailgate/bumper on your car is more to do with the aerodynamic flow in the area, or possibly active regenerations of the DPF.

DPFs don't remove ALL particulates. A commonly given figure is 80% reduction (AA).

I always use vmax when I can, so not sure that will help, but thanks for the info.

I do approx 20k a year, maybe 15k ish on the motorway, so it's not like I'm doing lots of short journeys to clog things up...

As to 80% not sure that's true.

All the dpf specialists that I have spoken with have told me that I should have no soot.

Equally the Hyundai garage verbally told me that Hyundai euro have not experienced this issue before.

I think that the car has a defective dpf. The mot smoke test that has been used to say the car is ok will also pass a car that has had a dpf delete. So that gives me no confidence.

Basically I think that they have plug in the "computer" and it has said "no problem".

I understand that it's hard to detect mechanical problems in this day of computers having all the answers....