So my engine does this ticking/clicking sound which occured recently. After changing the engone oil, mechanic told me they found some shavings in the old oil. Also im experiencing a 20l/100km while driving really really gently in the city which i also thought its a bit too much? especially when its said to do 13.9/100km officially so i thought that 6 liter difference must be a little too much? Maybe its connected somehow?

Anyway... anyone know what could be the cause of this sound? (video attached)

Shavings in the oil is what I would be worrying about first, the cliking sound will likely be found when you get the answer to the first question.

What kind of shavings ?
Did you get an oil analysis done on the old oil ?

I dont really know, the oil is probably long gone by now lol. My mechanic didn't specify and I didn't think of asking, just told me they found some metal shavings. He told me it might be needed to disassemble the whole engine to find the cause of this which isn't ideal. But hes not specifically a mercedes mechanic so I thought I might try asking elsewhere about it..

I wonder if its possible that theres some superficial part thats causing this or if its something that reqiures disassembly of the whole engine.

The M278 engine is very complex and you dont just start taking it apart to look for an issue. Not some american simple V8. Many mechanics on Youtube express it can be very hard to work on. Best to do shorter interval oil changes and care for it than to fix it. Metal shavings is oil is horrible. It will not be simple or small. You need a German independent mechanic or the dealer, not just any shop.

Yep, Im assuming previous owner didnt change the oil in time... but now I have the consequences to deal with and we dont have a mercedes dealership in the area.

Best of luck to you. The best thing you can do at this point is frequent OCIs. Tearing down an M278 and replacing parts will cost more than a replacement used motor.

ovd, sorry for your MB problems. Not that it matters now but how many miles are on that engine?

Thank you. By the way, now my technician added castrol 5w30 which is not what MB recommends, but he said it should work just as fine. But is it really? Because on other forums I mentioned it and some guy who works in a shop suggested to replace it asap because it could cause more metal shavings as it is too thin. So now im totally confused

That vehicle has nearly 186k miles, but I bought it only because the engine was replaced with a 37k miles engine.

Mobil 1. 0-40 is oil of choice. 40 weight not 30 weight.

I know it but now its already too late so Im thinking should I keep driving for a bit or should I change it immediately. Its so annoying, from now on Im only visiting MB specialised technicians.

At this point the only way to determine what might need to be repaired/replaced is to do an oil analysis at a legitimate lab. That will require you to do an immediate oil change to get the required sample. And the will also enable you to put the proper oil in the engine. Once you have the results of the lab analysis you will have a better idea of the source of the shavings. It is also remotely possible that the shavings are remnants from the work done during the engine swap. Good luck!

This, need to know what kind of metal is in the oil. Could be bearing material...

Visible metal in oil means the engine is done, my guess excessive bore scoring with bearing play at this point you can keep driving it until it breaks and then replace with a used engine. Do not attempt to repair engine as that will result in a higher cost and very few people can get them right.
On a normal car you could use 30 oil under cool conditions and light driving habits but why would you?
On an engine in it's last legs going with 50 might help reduce oil consumption and help it last a bit longer.