I went through the same thing last summer, I put Mobil 1 synthetic in and the engine was noticably noisier.
I couldn't take the difference and soon switched back dino oil.
I had to ask myself, if I hear more noise, what is causing it? Parts moving around and having greater tolerances with the sythetic?
I felt much better going back to dino, after all, that is what the factory intended for this engine.
BTW, you might read up here on Chevron Delco (?), it will keep the insides nice and clean while providing great overall performance, all the Diesel guys love it but it can be run in ANY Mercedes engine. As a plus, Costco stocks it.