I've had excellent results running the Amsoil 10w-30 and now 0w-30 in my 2002 Audi TT roadster, with the 225 Hp version of this engine. I like them both better than the Amsoil 10w-40 I first tried when I got this vehicle last year. I'm seeing about 3% higher fuel efficiency with the 0w-30 than I did with the 10w-40 and oil consumption is exactly the same - approx 1/4 qt every 3000 miles.
I don't see any advantage of running anything heavier than a 10w-30 in this motor, even if you live in an extremely hot climate. If I was using Mobil 1 in my vehicle, I'd run their 10w-30 year round, with a 6k-8k change interval, depending in the severity of driving conditions.
The OEM transmission fluid is a GL-4 75w-90 synthetic that does only has to be changed about every 100k miles. Both the Amsoil Series 2000 gear lube and the Redline MT-90 gear lube work very well in this application.
The OEM coolant is a excellent, long life product that I'd change whenever the timing belt gets changed in your engine - say every 60k to 90k miles.
The OEM power steering fluid is a PAO/Ester based synthetic. There is no change interval recommended, but it's a good idea to suction the fluid out of the reservior every 75,000 miles and refill it. Run the car for a week and repeat this process. Do this about three times and the fluid will clean up considerably. This will extend the life of your PS pump and all the seals in the system ....
The wheel bearings on this vehicle are sealed and do not require any normal servicing ....
I buy common replacement parts @
www.audiquattroparts.com.
Tooslick
www.lubedealer.com/Dixie_Synthetics