So far the members have adroitly avoided your question about the soot. MBZ lovers seem more into oil changes and Italian tuneups. Lets get down to soot.
Diesel fuel produces much more carbon (soot) than similar amounts of gasoline when burned under similar conditions.
An origional German plot by one Herr Diesel uses heat resulting from very high compression to burn cheap stuff that spark plugs won't detonate, like most any flammable oil with a btu content above cotton seed oil (Crisco and Mazola Oil got me and my VW Rabbit Diesel home a few times in my "youth" when diesel pumps were scarce).
Note: MBZ requires conventional Diesel fuels if you want to get more than the 88k I got in the VW.
Anyway, Herr Diesel's technique results in an efficent, though rather nasty, combustion of cheap fuel with lots of soot left over. The essential high compression blows much of this soot past the pistons into the crankcase and garbages up the oil. This requires the mandatory use of the special motor oils rated for diesel engines like Aaron and VA300SD use and reccommend.
Diesel rated motor oils have the essential additives that will trap the soot, keep the engine clean, passages clear, keep smoke emissions down, etc. But one MUST change oil frequently. Each 3000 mi is good, unless you want 88K like I got on my first diesel.
I too recommend the Red Line fuel addative appropriate for your model engine.
240D 299K miles
[This message has been edited by Roger (edited 12-31-1999).]