I have read about the sludge build up problems with these engines and wondered if some years were worse than others or was this always a problem?

The car I'm looking at is really clean and priced about $2K below KBB but the underside of the oil cap has some sludge build up (car has 97K miles).

Is it safe to assume that if the oil light is not coming on and I remove the pan and turbo oil return hose for cleaning, frequently change the oil, I should not have the sludge problem?

Also, does anyone know the cost for a junkyard engine?

Also, is there a system that detects the octane rating in the fuel or a knock sensor on the engine? Reason I ask is b/c I would guess past owner did not run premium fuel.
Thanks

 

If the engine is still running well, pull the oil pan and clean theoil screen. If there is sludge there also do the valve cover.
The car has a knock sensor and can run on 87 octane with poor performance.
After cleaning the engine, use a synthetic oil.

https://www.audiforums.com/m_16044/tm.htm

 

I put 1/2 a bottle of seaform in my crankcase and ran it for about 75 miles before I changed my oil... took out a lot of the sludge that was built up in my 98.

 

How many miles were on your car and how frequently did you change the oil? Also, did you happen to notice the underside of your oil fill cap - did it have any build up at all on it before the cleaning?

 

I just bought the car.. the oil was changed regularly but I dont believe the previous owner ran full syn... I have 122k on mine and it runs fine. My oil cap DID have build up, now it doesnt.

 

The earlier the car the worse the slugde will be as they ran regular oil and the smaller filter for a longer time. So in that reguard 98 is a bad year. I have a 98 and havent seen any issues but i know the car was maintained properly. Dont worry so much about the return line. Its huge and the likely hood of it being pluged is small. You need to worry about the turbo pressure line and the oil pump pickup. All the other lines are just wishfull thinking by audi engineers. The biggest reason there is a sludge issue is the fact that they left the secondary coolant pump off the a4. The s4 and a6 with the 2.7 have one and they run regular oil without sludge issues. The tt and a bunch of vw's run the transverse 1.8t WITH a secondary coolant pump and have no issues. So the best way to prevent sludge is to allow proper cool down time for the turbo. Let it idle for 20 or 30 secs before shutdown. Also dont drive hard the last few miles of your trip. Thats the key to sludge avoidance.

 

Quick question on this, where is the best place to get the bigger filter? and does it matter brand wise if other brands make them?, also what weights/oils you guys recomend to switch to. All i know is the dealer had always done the oil changes and on time with the smaller filter and reg oil. Its a 99 with 86k miles so i figure i might as well switch over now cause its due for one in a few hundred miles. Thanks guys.