Thanks for reply(s). Forgot to mention the non-mercedes dealer had oil all over the place by changing via the drain plug...thought there has got to be a better way!! Also appreciate the concern about sludge and other particles left in the bottom of the oil pan...also a concern of mine which was answered. My ML55 uses synthetic oil and the oil filter case in on top right-side of engine; may have to also purchase one of those oil filter tools? Got a good deal on a few cases of 5W50 oil, and filters throught the internet, about ready to undertake oil/filter change. In my earlier threads the question was put forward about more frequent oil changes than FSS and the feedback was excellent. You can probably tell I am a novice Mercedes owner and this forum is the best place to raise questions and get honest and reliable feedback. Many thanks.