I asked the service advisor before and they (dealer) not telling saying this is a complicated process and need special tool(s).
check out the youtube and I tried it and it work when I don't need to bring to my dealer for $CAD 300 ++ nett oil change.
press the phone and ok button on the same time and you will get a diff menu on the dashboard.
The C300 took about 8.5 L of Mobil syn oil and cost me about 40 bucks for the MB oil filter that I bought from dealer part dept.
Took it to my local garage and my mechanic going thru the same steps as recommneded in the manual and he only charge me 100 bucks with oil and labour. (I supply the filter)
for those of you that need to change oil or find a better service than the dealer....there are way and there are light out there