Phiber Optik

Hello, I have been battling with an oil consumption issue with my wifes 2011 ML-350 bluetec for some time now, the low engine oil light will come on 2x between ~10,000km oil change intervals, each time we top up the oil with 229.51 spec oil. After several trips to a mechanic for diagnosis they advised it was the crankcase breather diaphram/hose which I replaced and has made no difference. There are no apparent oil leaks (no stains under the car) and no visible smoke from the exhaust (assume this is caught by the DPF). Does anyone have suggestions on similar issues they have encountered?

kajtek1

2x would make 4l addition?
That is still within specifications, although usually MB engines burn less.
Lack of oil stains under the car doesn't mean much. Did you check belly covers?

Phiber Optik

We have had this vehicle for almost 2 years now and it didn't consume any oil for the first few oil changes, now it is consuming at least 3L x twice in less than 10,000kms. I have removed the belly pan and it is dry, also the mechanic performed an UV oil dye test and said there were no external leaks.

kajtek1

All you can do at this point is clean crankcase ventilation system.
Other issue might be your turbo seal leaking oil into intake, what will eventually burn it.
Still 3l for 10,000 miles is not much, so I don't think you want to rebuild engine becouse of that?

Phiber Optik

it's over 6L in less than 10,000KMS (6090miles) (over 3L TWICE per oil change interval), which is unacceptable and is not normal as the vehicle didn't consume ANY oil between 10,000kms oil change intervals previously. The vehicle has an aftermarket warranty and I would like it fixed as the expensive oil is starting to add up, but the mechanic is having a hard time figuring out the issue. in my opinion it is either the turbo oil seal, piston oil control ring or valve stem seals.

kajtek1

We had long topic inW210 section where 1 of the members had similar issue. He took it to a dealer and start records.
Turned out MB does allow for hefty oil consumptions (I remember like 1l for every 1000 miles, or something in this range), so even he was pouring lot of oil in it, his complain was not accepted.
Took couple of years to discover that his valve cover was leaking unnoticed and oil was just evaporating/burning without outside trace.
So good luck with your case.

Towmater

If you pull your intake Y, is there oil sitting there in the turbo? You could also, rev it like that and have someone check to see if oil is spraying from the intake. I had a leak in my turbo and it used that much. All this is assuming of course that nothing is leaking externally.