Pho Q let me see if it needs to be replaced.

Not sure if you've checked out www.idparts.com/ but they have a good selection of oils that meet the required specification. There are tons of 5w-30 oils out there, but few that meet the 229.52 specification required of this engine. My understanding is that failure to use these oils (all seem to be German made and unavailable at local auto stores), will cause DPF issues with time. Interestingly, when looking to purchase a preowned GLK I came across 2 with DPF-related check engine lights, and sure enough they were not serviced at the dealership. I assume they took the cars to a Jiffylube etc and ran a US-made 5w-30. I have been using the standard Rowe offered by IDparts, the price is reasonable.

Manual says MB-228.51, MB-229.31, MB-229.51 for the GLK250 (651 engine). Canadian Tire recommend 5w40. I'm using 5w30