When accelerating the engine when it is cold I get a faint valvetrain noise that persists for a few minutes until the engine is warmed up a bit (though not at normal operating temperature). Are M103s like this normally? The car is quiet at idle when cold, it is only until the car is under acceleration that I can hear the noise. I'm using Rotella 15W-40 and something is telling me that this might be a bit too thick.

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1989 300CE