NCT fail - too much oil - DPF

[JohnC]

So my dads 2008 520d failed as they couldn't test emissions due to too much oil.

So I drained about a litre off to get to the MAX level.

After getting a call from my friend just as I finished I said what I was at and he mentioned about the DPF could be clogging up and they puts pressure into the oil system which would make the oil level seem high. Is this true?

Any way to test this out?

My dad's friend owns an SIMI garage and is trusted in the ability to fill oil. Very unlike him in his eyes.

[HealyC]

Yes more than likely the dpf is partially blocked. Car has to regenerate the dpf to clean it out. One of the ways it does this is that it overfuels at certain times to ignite the excess fuel in the dpf. This cleans it out as the temps go over 800 Celsius. If the dpf is too blocked to regenerate the excess fuel will be forced past the usually the piston rings and "tops" up the oil level.

How to fix it. Change the oil and filter as now it has some diesel in it. Then drive the car hard up the motorway at a constant speed of about 70-80kmh.

If it happens again then you need to see a) if the dpf is blocked and b) why it's blocked.

[JohnC]

Lovely. Thanks Conor

I saw on another forum to keep at 3k revs ie 4th gear for 20minutes

Dad won't be too happy now ha