There is a technical bulletin from Audi about the sludge problem we are having,and here is the list of recomended oils.

Castrol, Castrol Syntec 5W-40
Chevron, Chevron Supreme Synthetic 5W-40
Elf, Elf Excellium LDX 5W-40
Kendall, Kendall GT-1 Full Synthetic Motor Oil 5W-40
Mobil, Mobil 1 0W-40
Pennzoil-Quaker State, Pennzoil Synthetic European Formula 5W-40
Pennzoil-Quaker State, Pennzoil Synthetic European Formula Ultra 5W-30
Pennzoil-Quaker State, Quaker State Full Synthetic European Formula 5W-40
Pennzoil Quaker State, Quaker State Full Synthetic European Formula Ultra 5W-30
Seventysix Lubricants, 76 Pure Synthetic Motor Oil 5W-40
Texaco, Havoline Synthetic 5W-40
Total, Total Quartz 9000 5W-40
Valvoline, Valvoline Synpower 5W-30
Valvoline, Valvoline synpower 5W-30