I was putting groceries in my new (3,600 miles) C230 coupe and happened to look down at my tailpipe. I saw a bunch of soot collected inside the tip. i wiped my finger around inside the tailpipe, and sure enough it was sooty. It doesn't seem to be getting bad gas mileage or anything. Is this abnormal for this car? I would expect to see a light grey deposit, maybe. But nice black carbon makes me think that it is running rich. Should I take it in to be looked at?? I am tempted to wash it off with a little gumout and see if it comes back. What's everyone think?