Mercedes-Benz service agents may say it doesn't need changing (or only at 100,000), but if you want your car to work better and last even longer than Benzes often do, the general consensus at MBworld.org and Benzworld.com is to service the supercharger every 5 or 6 years or 50 - 60,000 miles. I bought a C230 Kompressor and the fluid had never been changed... it was thick and black, and smelled horrible - it CLEARLY needed changing. You MUST use Mobil Jet Oil II, available from the dealer or airplane service centers.
Same for the transmission... they used to say the fluid "never" needed changing, but now they've backpedaled on that to say it may need changing every 100,000 miles under "severe" conditions - which is to say, normal city driving. Consult your dealer.
Refer to the official Mercedes-Benz service recommendations in the pamphlet linked to below for ALL up-to-date info on products for your vehicle.