This topic has been covered before, but I highly suggest using the red-orange MB coolant. The previous owner of my 300D used that green crap, and not suprisingly the radiator became plugged. Why give you Mercedes anything less than what it deserves? Buy the stuff from the dealer.
1976 300D (W115) - 330K and still going (sort of)
1991 300D 2.5 Turbo - Sold at 221K
1983 280SEL - Sold at 206K
1981 300SD - Sold at 232K