Well, I agree with Gilly, it's difficualt to diagnose sounds via e-mail, but there are a few things to think about:
1. Knocking, as it detonation, is handled by the "knock sensors" that your car is equipped with. It automatically retards the timing to get rid of the knock. If detonation is indeed your problem, you'll need to try higher/different octane gasoline. Our 190E 2.6 HATES a certain brand of gasoline, and I found out it's high in sulfer and they often "fudge" octane ratings.
2. Oil pressure problems are unlikely, but could be really troublesome in the long run if that is indeed your problem.
1998 C230 "Black Betty"