I had one of these valves on my old Mitsubishi Montero and I must say that it worked very well. It had had a nipple to which I permanently attached a short hose. This made it easy to drain directly into a container. It never leaked even so much as a drop.

Newer MB's are all intended to be drained by vacuum through the dipstick opening. This actually removes more oil than opening the drain plug. You can get a variety of inexpensive oil suction devices from boating supply houses (real hard to get under those inboard motors :-).

Alan
63 230SL
96 G300DT
98 E300DT