High oil consumption, 2010 ML350 Bluetec OM642



Does anybody have any other suggestions on things to check or try?
The PCV valve was replaced by me last year, then again during the emissions modification apparently. Either way it's newer and the latest updated version.
Here's my plan:
Remove the splash shields underneath and watch for leaks. I pulled them yesterday and they seem pretty dry. Also had a bunch of seed husks thanks to our local rodents.
Change air filters (I changed them last year 6000 miles ago)
Oil change (it's due)
Install ProVent 200 oil catch can to see how much oil is getting past the PCV valve
Try some sort of Motor Medic, MMO, etc to see if I can remove the carbon from the rings
My theory is that I have stuck rings, or worn cylinders. Last year when parts were backordered it was running the regen cycle very frequently, and I'm wondering if it washed too much oil off the cylinder walls. I sent the oil to Blackstone for analysis and it came back with high fuel levels in the oil.
Are there any engine treatments anybody recommends to try to unstick the rings? I'm generally wary of snake oils, but figure it's worth a try.
Should I get a compression check?
Any other ideas?
We really like the ML, it meets all our current needs, but if I can't fix this I will probably trade it in and get a gas version or a minivan.
Thanks!
Ian
Portland, OR




A quart in 300 miles is a lot of oil. I doubt it's leaking; you'd have a lake of oil under the car. Check the compressor wheel of the turbo for oil leakage.
I did the bluetec recall which changed tons of parts including the pcv valve but no avail.
Mercedes dealer wanted to charge 600 just to diagnose excess oil consumption, why pay to find out about an issue I already know about?
I did hours of research on this issue and I have a thread on mbworld about this exact problem on the R class forum.
My research suggests it is almost certainly the piston rings. There is no blue smoke coming out our exhaust pipes due to the dpf and SCR (adblue system).
Sell the car, it's not worth chasing.
I sold my r class very cheaply because I was so irritated by this issue. If you are madly in love with it, put rotella t6 heavy 15w40 oil, maybe less oil will slide past the rings if its heavier.




T6 meets MB spec 228.31. If that's OK for your engine then it's a good oil, readily available and reasonably priced. (Looks like you need 228.51, unless you don't have a DPF)
Last edited by John CC; Nov 3, 2023 at 07:55 PM.

If the rings are blowing by enough to burn thru a quart every 300miles it should be blowing by when you remove the oil filler cap. Regardless changing oils to a thicker oil if you will wont do squat to combat the oil loss. Change oil types if you want (I have no qualms about that) but if you are going to fix the vehicle take it to a independent and have it checked out.
Also if the oil is actually burning off that quick your DPF is gonna get clogged up much quicker than it should. If its going down the tailpipe I am surprised it hasnt already. Do you have a monitor that can track regens?
T6 meets MB spec 228.31. If that's OK for your engine then it's a good oil, readily available and reasonably priced. (Looks like you need 228.51, unless you don't have a DPF)
Last edited by tjts1; Nov 4, 2023 at 12:46 AM.
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I did an oil change a few weeks ago, using Costco diesel 15W-50 and also added some Seafoam to the oil per the instructions (I had some on hand). We drove it about 300 miles, and it still burned about a quart of oil over that time. So I did another oil change with the recommended Mobil 1 5W-30 ESP, and have about 90 miles on that so far. We luckily don't drive the car that much these days since we got a little electric Fiat 500e last year. But the heavier oil didn't seem to significantly slow the oil loss.
So I was thinking I'd try to put about 1000 miles on this oil then try the Liquimoly engine flush treatment.
I also installed a ProVent 200. After 300 miles it hadn't collected any measurable oil, but did collect some water. Interesting.
That has me wondering if the turbo is leaking? Or possibly the oil is getting past the rings and burning so not showing up in the PCV system.
I have also been considering putting something straight into the cylinders and letting it soak to try to free up the rings. Also putting a scope in there to see if there is any crosshatching on the walls. Is the injector the easiest route to getting in to the cylinder, or the glow plug? Neither sounds like fun.
I will keep updating as I find more. I'm also researching new cars, but don't want to spend the cash at the moment so hoping to limp this along for a bit longer.
(Edit, 300 miles, not 30. Updated above)
Last edited by Carcheologist; Feb 28, 2024 at 03:00 PM.
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I did an oil change a few weeks ago, using Costco diesel 15W-50 and also added some Seafoam to the oil per the instructions (I had some on hand). We drove it about 30 miles, and it still burned about a quart of oil over that time. So I did another oil change with the recommended Mobil 1 5W-30 ESP, and have about 90 miles on that so far. We luckily don't drive the car that much these days since we got a little electric Fiat 500e last year. But the heavier oil didn't seem to significantly slow the oil loss.
So I was thinking I'd try to put about 1000 miles on this oil then try the Liquimoly engine flush treatment.
I also installed a ProVent 200. After 300 miles it hadn't collected any measurable oil, but did collect some water. Interesting.
That has me wondering if the turbo is leaking? Or possibly the oil is getting past the rings and burning so not showing up in the PCV system.
I have also been considering putting something straight into the cylinders and letting it soak to try to free up the rings. Also putting a scope in there to see if there is any crosshatching on the walls. Is the injector the easiest route to getting in to the cylinder, or the glow plug? Neither sounds like fun.
I will keep updating as I find more. I'm also researching new cars, but don't want to spend the cash at the moment so hoping to limp this along for a bit longer.
Sadly MB decided to prescribe oil which is good for your DPF, not so great for your oil control rings. I've seen the same story over and over. There is no solution besides replacing the rings. 229.51/52 oil kills OM642s.
Last edited by tjts1; Dec 13, 2023 at 11:00 PM.








Note the reference to a special oil filter. If you decide to try this I would recommend one or two filter changes during a 5000 mile OCI.
Last edited by John CC; Jan 2, 2024 at 09:45 PM.
Sadly MB decided to prescribe oil which is good for your DPF, not so great for your oil control rings. I've seen the same story over and over. There is no solution besides replacing the rings. 229.51/52 oil kills OM642s.
I did the bluetec recall which changed tons of parts including the pcv valve but no avail.
Mercedes dealer wanted to charge 600 just to diagnose excess oil consumption, why pay to find out about an issue I already know about?
I did hours of research on this issue and I have a thread on mbworld about this exact problem on the R class forum.
My research suggests it is almost certainly the piston rings. There is no blue smoke coming out our exhaust pipes due to the dpf and SCR (adblue system).
Sell the car, it's not worth chasing.
I sold my r class very cheaply because I was so irritated by this issue. If you are madly in love with it, put rotella t6 heavy 15w40 oil, maybe less oil will slide past the rings if its heavier.






We have just over 1000 miles on the ML350 since my last post.
I'm running the usual Mobile One 5W30 ESP that meets the MB 229.52 spec. I have been waiting for the car to tell me when the oil level is low, which I believe is when it's down about 2 quarts. I will double check the dipstick when it happens.
But I checked it yesterday after it hit 1000 miles and the oil level is right in the middle of the dipstick, so down about 1 quart.
I haven't had a chance to check the oil catch can yet, but plan to when it dries out for a couple hours.
So again I ran some cheap 15W40 diesel oil for 300 miles with 8-9 oz of Seafoam for 300 miles. Then changed the oil and went back to the usual Mobil One ESP. I also added a Provent Catch can at the same time.
I have never seen the oil as clean as it was after the second oil change. It didn't turn black immediately like usual, making it harder to gauge the level when refilling. But even if I overfilled it slightly it's well past 500 miles per quart.
I'm obviously keeping an eye on the oil consumption, but if it continues like this I can easily justify keeping the ML for a while longer. I'm happy to add a quart of oil every 1000 miles. Even 500 miles given how little we drive it. But 300 miles was definitely concerning.



Note the reference to a special oil filter. If you decide to try this I would recommend one or two filter changes during a 5000 mile OCI.
But I will also keep an eye out for that Valvoline oil, at the moment it seems to be unobtainium.















You throw it in right before the oil change and let it run for half an hour or so, then drain.


