I havent been able to find anything online to answer this so hoping someone can help. I purchased a 2009 A6 with 2.0T motor. Had it about 4 months with no issues when engine warning light came on. Mechanic said PCV valve needed replacing so we had that done. Now the car is using a litre of oil every 1300km. Everything i read suggests PCV fixes oil use, not creates it. Anyway the valve has since been checked and all ok and mechanic doesn't know what could cause it. Any suggestions?

 

Are you seeing smoke (blue/white) from the exhaust? Also check the PCV by doing this. Crank the engine and while it's idling, remove the oil filler cap from the engine but to not remove it just yet. Slowly pull up on it as to remove it. If you feel it being sucked back down onto the opening, the PCV valve is NOT working like it should.

 

Thanks for the reply dave944. No smoke from the exhaust. Oil filler cap doesn't seem to have any excess suction. Motor runs really rough though when filler cap is removed, not sure if that's normal (probably)
The mechanic that replaced the PVC valve has since replaced another (expensive) part on Audi's advice (couldn't tell you what it was called but apparently related to PVC) but still same issue and he's confident PVC is working. Very frustrating as it's becoming an expensive exercise.

 

If it's running rough when the cap is removed, the PCV is not working properly. The PCV valve is supposed to close at idle (when manifold vacuum is the highest). When you open the oil cap and the PCV valve is open (at idle) too much air is being sucked into the intake and causing to run rough. However, I think your engine has a more complex crank case vent than just the round diaphragm types like on some other Audi engines. Thus a more expensive part.