2004 A8L engine sludge?
 

Yesterday I picked up my car (04 A8L 85K miles) from a shop where it had the front wheel bearings changed and within 1/2 mile the engine started chattering like a diesel and the OIL CAN symbol popped on the screen.
Stopped the engine, checked the oil, looked full.
Stated the car, chattering not there and no oil dummy light.
As soon as got on the road again once RPMs hit 1700-1800
OIL CAN was on the screen again.
Checked the oil again, still full.
This morning started the car, chattering is there and no OIL CAN ICON, untill engine revved up over 1500 RPMs.
Since I've had the car I've changed the oil and filter every 5K using Mobil 1.

Should I SEAFOAM it or is it too late?

Any help would be appreciated

Was teh timing belt done at or about 70k? If you can't confirm 100% that it was, you might wanna NOT drive it until you can get that done. If that belt goes, and it sounds like it might be on uts way there, you are looking at a full rebuild. Not cheap!

Thanks for the input AWDaholic
Are you suggesting that the timing belt runs the oil pump in the early 4.2s?
In case I wasn't descriptive enough it seems to me that the valves are not chattering because of timing issues but because of poor lubrication.

Most peeple call me "Jazz."

Well, the chattering without the oil light suggests it may not be an oil availability issue. The only other thing, that *I* can think of, that would make the valves chatter is timing. Of course, I am only a shade-tree mechanic. NOT a certified one. The two best guys I know of, based on personal experience, and, from what I've seen around the boards, are auditech79 & R.A.I. Motorsport. PM either one of them your symptoms and you'll have teh best answer anyone short of Ingolstadt can give.

Sludge isn't a common issue with the 4.2L engine. The oil light you're seeing can be two different things. A yellow warning light indicates its low, a RED light is pressure. If you are seeing a red oil light something is up. Either the pick up tube in the oil pan is clogged, oil pump is shot, or the oil filter is plugged if you used a cheap one without an oil bypass built in. I would change the oil filter, seafoam or use an engine flush, change the filter again and put in fresh synthetic. If that doesn't get your oil pressure back there will be more diagnosing to do.

P.S. Don't drive it until you can verify the oil pressure is good.