One must remember what the original question was......
Yes this is a very popular subject for debate, and I have studied this thing for a long time, but there can never bee to much debate, however this posting has taken the way of many offramps, so it has lost some of its intent.
Just some clarifications for all...
1. The benz manual is useless in telling you much of what to do about an oil change. My 98 Manual is proof of this. ( So it is okay to ask)
2. Yes it is true that it is not a good idea to use diesel oil in gas engines. ( Plugs will foul)
3. Dont try to compare diesel vs gas unless you know the difference's, it will save embarrasement.
4. 20W-50 is a little heavy for Chicago's winters.
And here is something that the new 98 diesel engine owners will find interesting, I have found out that over a period of time the viscosity index will actually increase, due to the accumulation of soot in the oil. This is only on the new engines.
5. Knowledge is Power, it's up to you to apply it.
A very slippery subject indeed
All pun intended.
98 300 DT