What type of oil & how often are you changing?

Mobil 1 0-40 European Car Formula is the MB recommended oil. May as well use that.
Cheapest i could find in the US is at (W)almart 5G jugs.

I am with Cedes on this one.
Just changed the oil at 6K. I am sure the additives are more than adequate for the dealer
recommended change interval, but I do not trust that the filter adequately removes all the abrasive particles that accumulate in the oil over time. ( (combustion blow-by, all that stuff that makes the oil darken over time) The filter and the oil costs $40 total , and I am certain it does not hurt. Plus I did it just to see how hard it is, now I know it is an option.
The filter is behind the engine on the left. You need a 27mm socket wrench w a long extension piece to get at it. I used a vacuum oil extractor to avoid dealing with removing the belly panel and having to buy a new crush washer. The filter is an MB dealer item, right now. When the filter housing cap comes off, it brings the long plastic centerpiece with it, it is clipped to the housing cap , the actual filter can be just pulled off the center piece.

Just to clarify: once the oil filter housing cap is off, you will see a large black plastic spike
sticking out of the middle of the filter. The cap snaps on to this plastic centerpiece.
You can just pull it off the cap (takes a bit of force) , and then you will be to slide the actual filter off of the plastic centerpiece.

To get the rubber o-rings off, I use a flathead screwdriver, with the blade wrapped with
hockey-stick tape, to avoid scratching the plactic.