Om651 bluetec oil dilution (oil level increase with diesel)
I have a mercedes. C class with om651 bluetec euro6 c220 170hp form. Problem is that the oil level is increasing. i changed oil 3000km ago and level increased from middle of dipstic right to the max. So right now is at the max. ( measured on flat ground with cold engine overnight)
Car has under 200k km so not a really high mileage car. Car runs good, no smoke, pulls fine, no vibrations or other issues. Exhaust is clean, no errors. Scanned it with a generic diagnose and dpf differential pressure is good, injectors look good.
I drive it dayli, usually 8km in morning and another 8 km in evening ( commuting to work ) and allmost each weekend i make a trip of 100km or more.
Oil seems to be thinner compared to the day i replaced it. I do not feel smell of diesel in it.
I plan in replacing again oil next week after just 3000km and just under 1 month... Original MB 229.51 oil +mahle filter.
Do you guys encountered this before? I recognize that i stopped the car 2 times when dpf was in regen ( felt heat and some burn smell when i stopped in parking lot) but is that enough to increase the oil in such short time? Is not my first car with dpf and never encountered this before...
I need some advice

Thanks in advance
Is it a possibility that there is water/ coolant in the oil?
Stopping mid regeneration shouldn't be an issue.
Water contamination should be detectable by presence of a whitish froth around the filler cap and obviously a drop in the level of coolant in the tank.
I just made a video. Injector nr4 seems to have some black dirt. Might be black death i was reading on forums? The copper seals from injector head can solve this problem with oil dilution?
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Not necessarily....you may need to look at the seats where the injector seals sit!
They may be pitted and replacing seals may or may not give you a short term solution.
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As above either injector is 'pissing' in cylinder (black death case where nozzle holder is cracked may do that, or then faulty injector), or continuous/too frequent DPF regen
Next week will go to a mechanic to check it as i think that i hear also the timming chain or something else that makes metallic sound. Idk if is real or in my head. The sound can be heard in the video also.
Is strange because i have checked it 1 week ago and all parameters were ok in the diagnostic tool. Dpf ok, injectors ok.
Will keep monitoring it...




Having car in garage, when I want precision measuring, I pull the dipstick 2 cm up the tube and leave it overnight. The following morning I stick it in and then read.
Not too many orings hold that well, so it is rare issue.
Mechanics know zip about oil testing btw.
Having car in garage, when I want precision measuring, I pull the dipstick 2 cm up the tube and leave it overnight. The following morning I stick it in and then read.
Not too many orings hold that well, so it is rare issue.
Mechanics know zip about oil testing btw.
I had the same problem reading oil level. Now Im following kajtek1's recommendations, pulling dip stick out and read oil level next morning.
Way to go.




Will keep monitoring it...
I have an employee who's from Romania. I'm a vodka drinker, but that SOB can drink me under the table with his mouth stitched shut!
I have a mercedes. C class with om651 bluetec euro6 c220 170hp form. Problem is that the oil level is increasing. i changed oil 3000km ago and level increased from middle of dipstic right to the max. So right now is at the max. ( measured on flat ground with cold engine overnight)
Car has under 200k km so not a really high mileage car. Car runs good, no smoke, pulls fine, no vibrations or other issues. Exhaust is clean, no errors. Scanned it with a generic diagnose and dpf differential pressure is good, injectors look good.
I drive it dayli, usually 8km in morning and another 8 km in evening ( commuting to work ) and allmost each weekend i make a trip of 100km or more.
Oil seems to be thinner compared to the day i replaced it. I do not feel smell of diesel in it.
I plan in replacing again oil next week after just 3000km and just under 1 month... Original MB 229.51 oil +mahle filter.
Do you guys encountered this before? I recognize that i stopped the car 2 times when dpf was in regen ( felt heat and some burn smell when i stopped in parking lot) but is that enough to increase the oil in such short time? Is not my first car with dpf and never encountered this before...
I need some advice

Thanks in advance
Sorry for my English!
This is known behaviour in some Mazda's engines. There is a additional fuel injection during negative piston cycle. This fuel is needed to help for dpf regeneration.
This additional fuel is catching by the piston rings and going into the oil. Probably the reason is your short city trips. At Mazda the dip stick have a second Max level. When the second Max level is achieved then need to change the oil immediately.
Best Regards,
Dimitar




i usually drink beer, wine or whiskey before checking the oil level. vodka is not my thing