The short rubber hose that connects between the PCV valve and the tube leading down to the crank case had collapsed and split, leaving the car stinking of oil, so I replaced it today. I was mostly focused on replacing the hose, but looked inside the PCV valve full of yellow colored goo, like what you'll sometimes find a little bit inside your valve cover at times. I'm presuming its oil/water condensate, and wants to be cleaned out. I bought the car about 18 months ago, and have done nothing to it thus far but struts, brakes, and oil changes. I'd driven many A1 and A2 cars up until this one, which is my first A3 car. I don't believe any of the previous cars had this sort of PCV valve on them. The previous owner worked three miles from home and had only accumulated 62K miles on the car when I bought it in the summer of '07, consequently, I doubt the car ever got fully warmed up most days and any condensate in the crank case never burned off and wound up in the PCV valve assembly.
I understand the purpose for PCV, but not the valve that this has in it... Is it just a one way check valve, or does it perform another function? How would I know if it was spent and needed to be replaced? I've seen notes on cleaning it with carb cleaner or brake parts cleaner -- something that won't leave a residue. Is there anything I should be checking? I did replace the air cleaner this summer (and the spark plugs as well -- and HATED that operation with a vengeance -- give me back my 1.8 and take back the cross flow head). There was no oil on the air filter as has been noted.
How does the PCV play into fuel mileage? I'd attributed the lower mileage on this car (28-32MPG US) to its larger engine and the slightly shorter gearing. I spin about 3400 at 75 MPH.