Originally Posted By: lucaq
It does suck, not sure that it caused the sludge, but I am not going to claim to be an expert here, if you could share some info on that I would be interested.
Not every Audi A4 / Passsat 1.8T is going to experience sludge, that's the good news. There are a number of factors that can lead to sludge however. Even with the larger size oil filter which Audi / VW now specify it still leaves the engine with less oil than in other 1.8T applications.
By upgrading to the Big Kahuna size oil filter you increase your capacty to around 5 quarts. Some options: Purolator L40316, Mann W950/4, Wix 51333 / Napa Gold 1333.
The PCV system is complicated and a pain to service. But it should be serviced on a regular basis because it can easily become clogged and restrict the flow of blow-by gasses.
Sludge, the black gooey kind, is something I have experienced myself. I chalked that up to driving habits which included a lot of short trips. I also had multiple vacuum / boost leaks which would have impacted the air to fuel ratio.
Carbon shards of coked oil can plug up the oil pump pick-up screen. When this happens oil pressure take a nose dive. The best approach is to drop the oil pan (another complicated procedure)and replace the pick-up screen.