Molybdenum additive is what makes that oil color I think. I guess airplane pilots swear by that compound keeping overheated engine from seizing. Most oil leaks with BMWs are on front of engine from what "Auto Repair Guys' YT videos have revealed. My 05 MB E320 CDI (om648.961 like yours) is closing in on 150k miles & recently went into low acceleration limp mode from M55 (port inlet shutoff motor) positioner fault so I tried a few Italian tune-up runs on highway & seems to have cleared up whatever was causing bind, Often majority of soot build-up will be in mixing chamber area of intake where intercooler hose plumbs into bottom of it so I might pull that hose down & see if I can't vacuum that area out. Maybe I'll try to make a video of that intervention & post it to YT.

Weird oil was that gray?? On cars with oil filters in the engine bay I usually suck up the old oil with a pump , that way I don't have to crawl under the car.

Appreciate all the Mercedes videos... Where do you got all the nm torque specs?

Are you still making videos?