Alright so as far as ive heard so far when people are worried about oil sludge they are just told to take the valve cover off or w/e and wait for the oil light to come on however I might have an idea on how to check for an early problem: Through VAG on the instrument cluster it will show you the status of your pressure switch... In the winter when i was running 5w-30 VAG and idleing would say the oil pressure is below spec but as soon as i stepped on the gas it would say oil pressure OK (and i never had an oil light). This summer i switched to 0w-40 and it will constantly say Oil Pressure OK no matter what the RPM.. Anyway after looking into this further the service manual says it will not set the oil light even if the pressure is too low unless the correct RPMs are met and depending on how low, met for a certain amount of time.

Engine switched off and oil pressure switch closed.
Coolant temperature less than 60 ° C, engine speed higher than 300 RPM and oil pressure switch open.
Coolant temperature greater than 60 ° C.
At engine speeds greater than 5000 RPM, an active oil warning won't be erased independent of oil pressure switch setting.

The service manual says that idle speed oil pressure should be 1.0 bar, however this is lower than what the switch says as ok, so the computer ignores the switch at idle. At 1.2-1.6 bar the switch is tripped and the computer says oil pressure is OK. It says the computer will only throw a DTC over 1500 rpms (i would guess that means turning on the oil light).

My point is knowing this, someone could look at the oil pressure switch and monitor how long it takes for them to increase their rpms to have the switch tripped and VAG to switch from oilpressure low to oil pressure OK, and if the amount a person had to raise their RPM's began to increase more than before (or maybe even idle) then they might have to start worrying about sludge? Any thoughts on this?

 

sludge shouldn't be a problem as long as you use synthetic oil and change the filter as well as the oil regularly, a DTC will only throw if there is a problem with oil pressure so it cant be turned on with VAG because it don't work like that you can only test the sensor to see if its working and you can only do the with a full working VAG licenced and would only be done with engine switched off ( oil pump have been an issue in the past for clogging ) im not sure if this was a recall

 

K well first, there have been long discussions where people have gotten sludge and oil lights even with synthetic oil changes: https://www.audiforums.com/m_602817/tm.htm auditech79 explains there, and what about for people who had previous owners change with reg oil and switch to synthetic. You cant get an exact pressure reading but you CAN judge based on if the switch is open or shut when you VAG the instrument cluster measuring blocks. The car doesnt need to be off to have the car tell you whether the prssure is high enough to close the switch, see what im saying, if the switch closes at 1.6 bar and your idle is 1.0 bar, knowing this you could see how long it took for your rpms to reach make the oil pressure reach 1.6 bar since an oil light will only be lit over 1500 rpms anything below sounds like it is ignored if there is low oil pres.