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Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22731
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Hi there I need help with my MB S320 2007, it is using too

Customer Question

Hi there I need help with my MB S320 2007, it is using too much engine oil with lower perfomance than normal.
Submitted: 5 years ago.
Category: Mercedes
Expert:  Matt replied 5 years ago.

The first thing I'd check is the crankcase pressure relief valve (PCV) these are sprung loaded and are only meant to 'burp' excess pressure every now and then. The exiting gas is piped back to the inlet , however should the valve stick open then the engine tends to suck the air out of the crankcase all the time and this carrys oil over with it.

If you remove the air intake pipe and look inside where the crankcase breather is plumbed in you may find evidence of oil.

If you do find oil replace the valve. If this is all OK then its possible that the valve stem seals are past their best and are drip-feeding oil into the intake. These can be replaced without removing the head by a competent garage in half a day or so

an engine flush may also help if you've got a sticking oil scraper ring so its worth a go, as for the oil if you go up a grade / use slightly thicker oil then this is less readily drawn into gaps and less likely to be burnt off

Customer: replied 5 years ago.

Hi Mat,


Thank you for your prompt reply.


Let me tell you a few other things about the car that might also help you find the solution.

I have recently changed the Particular Filter, EGR Valve, MA Filter, Turbo and Air filter (20k miles ago).


Recently perfomance has been revs going up (above 2 sometimes 3_at low speed (below 30 M/h), excess of white smoke sometimes,

sluggish around town and good performance at Motorway.


If you could please guide as my local MB is horrible and I have been frustrated with this car now for long time.


Thank you in advance for your help.





Expert:  Matt replied 5 years ago.
Hello William

do you have any check engine or other fault lights on?
Customer: replied 5 years ago.

No the car was in MB dealer to get the MAF installed and connected to the electronics.They have cleared all issues there and there was one coming from the MAF which they could not clear but said to me that code would not cause any problem because they road-tested the car and it was fine at the is no longer fine!!! It seems something simple, as you said PCV. What do you think?



Expert:  Matt replied 5 years ago.

do you know what that MAF code was?

also well worth taking a peek inside the intake pipe as I've suggested earlier