I totally acknowledge what's been said about the use of a (relatively) large amount of VIIs in oil, but I'll point out once more, while I do not track my car (A 2.8 12 valve would be tad slow
), I do drive it hard as far as street use goes. Why have I never had a problem with deposits? I did get those hard yellow/brown deposists in my '85 Buick's engine, which was on a diet of full synthetic 10W-30 (3k mi O/Cs). And I drove the Buick not nearly as "sporty" as the Audi. While I agree in principle with the theory of oil loaded with VIIs leaving deposits behind, I must wonder in how far the design of the oil system and engine contribute to general oil "health."
The other thing I'd like to point out, and it's something my mechanic found always odd, was the strange fact that the Syntec 5W-50 would not darken considerably over the first 5k miles. There was the theory, and I had that nagging suspicion, that maybe the oil looked always so clean, because all the nasties were deposited inside the engine. However, seeing how clean it looks under the valve cover, makes me doubt I'll find a lot of deposits in the combustion chamber or anywhere else. Even the bottom of the oil pan is pretty clean.
Also, as Dr. T mentioned, oils with a wide spread have been popular with some high performance Euro car makers, BMW even insisting on 10W-60 in some engine, and 0W-40 being factory fill in some Porsche cars.