Changed my oil today so I thougt I'd pass on a few things. First a question.
The 550, unlike some W209s, has a dip stick. It has "min" and "max" markings, and supposedly the difference between the marks is 1.6 quarts. The owner's manual says the total capacity with filter is 9 quarts. I ran the engine a bit at 7 quarts to fill the filter, then added 2 more. 9 quarts just barely reaches the "min" mark. So, do I trust the owner's manual and leave it at 9, or trust the dip stick and add some more?
A few notes:
The "B" size filter wrench from Auto Zone works perfectly - about $6.00.
The 550 does not have the long, needle-like thing that sticks out from the filter that you have seen in some DIY pictorials. But MB apparently uses the same filter for several cars, so you will have two leftover small O rings you will not need.
There are two large black plastic covers on the bottom of the engine. If you are draining from below, as opposed to pumping from above, you only need to remove the rear one - six 8mm bolts.
The drain bolt is 13mm, and is on the side of the oil pan, not the rear. I want to meet the engineer who put it there. It is right above and next to a stifffening member bolted to the frame (possibly cabrio only?) so that when you pull the plug oil gushes all over the stifffening arm and runs along the top of it so no matter how large your drain pan is you will get oil on your garage floor. Another reason to pump from above I guess.