I see that this is an old post, so maybe it has been resolved by now, but if not I will advise on some first up things to check and if you require further input please contact me.
The oil will only go two places, on the ground or out the exhaust. As you say there are no external oil leaks we must look a oil consumption internally.
Checking spark plugs will give a good indication if a particular cylinder is using oil extensively, Thick deposits will form around the central electrode and on the earth tab, if this is the case an internal problem with oil control rings, or valve guides and stem seals could be the problem, Check the air induction hose (turbo to inlet manifold) for excessive oil deposits, and with turbo's any fine oil deposits on the rear of the car, tiny black dots of oil, can indicate a faulty turbo oil seal and oil is being passed straight out the exhaust.
It may be a matter of the incorrect oil viscosity being used, check what oil is being used with what is recommended by Audi. Just a few things to go on with, so if you need more information please contact me, and I do apologize for the delay in responding to your post.
Friday, November 16th, 2007 AT 8:35 PM