sludgeing on 2002 Audi A4 Quattro

why is my oil crunchy?

Those engines have big lubrication problems if the engine oil is not changed frequently. I only use synthetic oil and OE oil filters.
2 more answers
is this a joke? Steve i thought you worked on imports
These engines are known to have sludging problems. This occurs when the oil is not changed frequently. First, the oil pressure system needs to be checked. Depending on results from the pressure test, we may recommend cleaning the oil system by removing the pan and cleaning the pick-up screen.
I can't stress this enough, oil changes are extremely important for these vehicles.