The dealer that sold me the car changed the oil with PennZoil 5w30 synth. I pointed out that wasn't an approved MB oil and they scoffed. I've since been using only Mobile 1 0w40. I must say though, the car ran much more quietly with the 5w30. My wife hates the sound of the engine. She calls it a 'wind up toy'. Now that I just ran out of my extended warranty...I'm going back to 5w30 synth. If it blows up I'll post pictures...but it won't.