Have your heard or read about sludge?
the vw 1.8 is well known for it I think.. I think its on the car bible web site.
recommends a full engine flush or somot... btw I'm just guessin...
http://www.carbibles.com/engineoil_bible.html
VW / Audi sludge problems
While the the 1.8T engines in Audi A4's, Audi TT, VW Passat, Jetta, Golf, New Bettle, are all very prone to sludge build-up, Audi/VW does not have an extended warranty for them from the factory. The factory warranty is 4 year/50,000 miles but it can be extended if purchased.
Although Audi/VW now has 10,000 mile service intervals, oil changes can be done between "services", and should be done if the vehicle is driven in heavy traffic, offroad, and non-highway use. Also, Audi/ VW will only warrant an engine if the customer has proof of all their oil changes