It sound pretty normal

Diesel oil is black by the time I check my dipstick when I am filling it with oil.

Now for the best oil for your car will start a heated debate although no one will dispute that you should be using a diesel grade oil in your 190d.

On the oil label are letters which speak of their ratingl. Loiok for one that at least has a CF rating or higher (CH would be higher)

THose oils are designed to suspend the soot (aka black stuff) that you are talking about.

There are alot of threads which go over this topic in great detail. I am not sure how cold it gets in dublin but here in chicago I use synthetic to aid in cold weather starts.

Just do a search on it and you will have alot more info


have fun

bob c