The truck is a 1999 ML320 US-spec gas engine. It was suggested to me at another post that the most likely culprit is the chain tensioner seal. At this point, I see no other option but to look further since I'm stuck and simply cannot identify the leak just by eyeballing the top and bottom of the engine bay. I was thinking of disassembling the belts, hoses, waterpump, etc. Oh and the leak cannot possibly be mistaken for coolant. In fact, I just changed the oil and I can see that the oil leaking is very fresh and clean oil.

Maybe this thread might help find your leak http://www.peachparts.com/shopforum/showthread.php?t=185729&highlight=oil+leak Scroll down in the thread for a photo of where the leak occured. My 2 cents.

By "chain tensioner seal" do you mean the timing chain cover gasket? The timing chain tensioner is entirely contained within that cover, so the tensioner itself cannot be leaking. Before you go tearing down the front of your engine, I would make sure the other post is referring ot the same motor that you have.