Originally Posted by Carson357

why not post a picture? i am willing to wager it is simply condensation, the residue that forms on the underside of the oil cap will have a yellow/light brown tint to it, the color is from the oil. is the coolant level dropping? also usually with mercedes leaks you get the opposite, oil in the coolant. also if there was enough coolant in the system to get on the oil cap you would have alot in the oil and i am sure when you pull the dipstick it would look milky by this point.