[ngoma]

You're good to go as long as the GP elements are not damaged, eroded, mushroomed.

We have to admit it, the diesel engine is a soot producer. There's going to be soot everywhere. In the oil, in the exhaust, in the combustion chambers, in the intake (where EGR), on the parking area, etc.

Your economy stats are great, that is the major yardstick I would measure the overall engine health by. When that number goes down, that is when you need to get concerned.

In fact that's what I do. Calculate the MPG each tank fill up. When the MPG falls, that's when I start looking for underinflated tires, dragging brakes, clogged air filter, state of engine tune, etc. 10-20% drop in winter is normal.