Ok i see lots of people having different ideas of what sludge is and how your engine gets affected even knowing your're doing all your maintance.
Fact one, synthetic oil does NOT save your engine from sludge, audi dealers use full synthetic required by audi for all A4 1.8T engines, the TT 1.8gets conventional oil yet never gets sludge. Why?
Fact two, using a larger oil filter does help reduce the chance of sludge but your're still gonna get sludge even using a full synthetic oil.
Fact three, the only reason why the A4 1.8T engine looses oil pressure and the TT 1.8T doesn't is the oil pick up tube design, the A4 has a lot finer screen that gets clogged very easily and hence looses pressure.
So using these facts why would you think just using a bigger filter and synthetic oil is gonna save your motor when the TT 1.8 uses conventional oil and a much smaller filter? The answer is its not, just about ALL of you that ownes a A41.8T is gonna get sludge no matter how good and how often you change your oil at some point. There are other factors in the PCV system affecting this but as far as the oil pressure problem its just the pick up tube.
Now in order to try and eliminate getting stranded on a long trip (usually happens) is to use a good quality synthetic, larger oil filter, and either using seafoam in the oil every 20k, or a full engine flush every 40k to try and keep the pick up tube as clean as possible. NOTE: this is only a preventitive, its still gonna happen to you, this will just help delay it and keep your engine from serious harm.
P.S This is a world wide TSB,ANY 1.8Tengine that developes oil pressure problems due to sludge and can show oil change reciepts up to the current mileage will get the repair free of charge regardless of mileage. Including free engine replacement if the damage to the engine is too severe.
Facts about oil sludge
