The oil that it takes is a fully synthetic Mobil 1 and the recommended weights are 5w-30, 10w-40 and 0w-40 wich is the best choice and recommended by Mercedes Benz. The ML 320 take 8 Qts. (2 gallons).
My personal advice is to use the Mobil 1 extended performance 5w-30 15,000 or one year wichever comes first for better protection IF YOU HAVEN'T GO WITH A HIGHER WEIGHT ONLY!!
Manual says 8.0 quarts(US) with a filter change.
The 2001 Mercedes-Benz SLK-Class has 16 valves.
The 2001 Mercedes-Benz SL-Class has 24 valves.
The 2001 Mercedes-Benz E-Class has 18 valves.
The 2001 Mercedes-Benz CL-Class has 24 valves.
The 2001 Mercedes-Benz S-Class has 24 valves.
The 2001 Mercedes-Benz C-Class has 24 valves.
The 2001 Mercedes-Benz M-Class has 18 valves.
5 quarts
8 quarts...
8.44 quarts
8.5 quarts.