Also, my independent mechanic has recommended Swepco 502 for my lifter problem in my '88 190d. He has never steered me wrong yet so...
Im gona put it in with my next oil change in a couple of days. I'll keep you posted of the results. For more info I found this link.
http://www.swepcousa.com/lubesite/add.htm
I am not in any way associated with SwepCo.