I have been religious about using the exact oil type recommended by Audi. I keep a case on hand. 501.01 spec oil. Currently I have Castrol Edge Professional OE . Covers VW 501.01,502.00,505.00. I found it hard to believe such a thing could make a difference but it was not worth a few bucks difference in price to take a chance. You also have to tell them it take 7.5 liters not 7 and not 8.

Mike