How to check for sludge ?

[Scott]

Wasn't the OP  vehicle about 40K in mileage?

What did the oil look like at inspection (dip stick) or oil change?

Records would help in theory but then again you could get records like this:

http://www.quattro123.com/A4TurboEngineWarrantyExtension.htm

Scroll down and check the photos about the "service records"

I'd go synthetic after a few dino flushes of about 2K with filter change to try and dissolve what's in there if you think its sludge filled.

I'd run it hot but do a long cool down too............

My 2 centavos, YMMV.
-Scott by BOSTON