Our 2013 has a small amount of oil in the air filter box, and just enough in the intake pipe to the throttle body to dribble out when tipped the right way. At 90k miles, could this be PCV? Few highway trips, lots of local driving.
If so, it appears there's valve/separator on the back of the engine. Anything else to replace? Can someone point me to a procedure, please? This is the M276 engine with the air filter in a box along the passenger's side and everything I've founds seems to be for an engine with two intake pipes and a filter in the front.
Thank you!

This is common on Mercedes and yes its the PCV system failing. Lucky for you and I we have the same engine and its a ***** to get at. If it goes bad all the way you will get a terrible squeal when the engine is hot. Not a easy job but not terribly hard but is a pain in the *** to get at.

Thanks! As yet, no squeal and no codes, but the oil in the intake is a pretty strong warning. There's also a bit of a smell of hot oil when the car's just been driven and pulls in the garage.

Some oil in the intake of a DCI injection engine is normal since there is no fuel in the intake manifold only air which allot are these days.

Faulty or clogged Positive Crankcase Ventilation (PCV) valve
PCV system function: The PCV system is designed to vent pressure and gases from the crankcase.
The PCV valve regulates the flow of these gases back into the intake to be re-burned.
Blocked valve: If the PCV valve or the associated hoses become blocked or clogged with sludge, pressure can build up. The pressure will force oil vapors into the intake system through alternative, unrestricted passages.

So the gasses and oil vapor goes into the intake to get burned.

Don't be overly concerned, this is standard for all these hot GDI engines to vaporize a lot of thin oil on extremely hot pistons.

The maintenance schedule for PCV + the HPFP that covers the PCV is indeed near 100 to 120k.Mi.
Mind you the same exact thing will still happen with all new genuine PCV parts... oil ingestion.

The collateral parts are the two upstream exhaust Lambda that get coated with oil solid contaminants. Good to replace after 80k.Mi.

Notice the M276 NA intake pipe has a built-in catch-can to capture the oil hoosing back out of intake plenum. Empty it annually.

Oh! Maybe that's my problem--I didn't know about the catch-can and have never emptied it. Can't believe I've overlooked it in the service items, but I'll check it. Maybe that's what dumped when I too the intake off--I detached the air filter box and intake hose at the throttle body.
BTW, if anyone knows the part number for those 4 screws that attach it, one was pretty chewed up by the time I got it back in and I should replace it.

not all service parts are sold individually... have a look st this web distributor:

mb parts source

I dont know your VIN.

Use this link to view all the parts diagrams for your specific model/submodel: https://nemigaparts.com/cat_spares/epc/mercedes/1/