Whats under the (sort of) valve cover?

[shortyb]

Did some maintenance on momma's 2020 VW Tiguan, 2.0 TSI EA888 Gen 3B with 80K. Replaced the oil separator/breather unit and snapped a pic while it was off. Cam lobes have streaks, but not any depth like wear would cause. Mobil 1 ESP 0W-30 for the last 25K, before that was Mobil 1 ESP 5W-30. Oil was NOT changed prior to removal.

Also replaced the spark plugs. They didn't look bad at all. 1-4 are R to L.

 

[JohnnyG]

Plugs appear to be running rich. Other than that, the engine looks pretty clean.

 

[QwikKota]

That looks like sorcery.

 

[KGMtech]

Was there a problem with the breather unit? or pre-emptive replacement? This might be related to the observation above about the plugs looking like a rich condition problem.

 

[Oillover]

Discoloration from repeated heating and cooling cycles combined with exposure to oil.
Since plastic is more porous than metal it absorbs the color of the oil and oil vapors, leading it to appear "stained" or have a film on it.

Nothing to be concerned about.

 

[shortyb]

Was there a problem with the breather unit? or pre-emptive replacement? This might be related to the observation above about the plugs looking like a rich condition problem.

No problem, VAG breathers are one of those components that are iffy and pre-emptive replacement (before something happens) is beneficial. When they go, pressure can build within the engine and blow out oil seals, causing leaks. Fortunately, they can give indications when they are about to go south. They have had about a bazillion revisions and are pretty decent these days though. Still, $100 part every 60-80K I personally consider routine maintenance to prevent problems.

The rich condition is typical VW in that it uses fuel to cool combustion charges and EGTs. Since momma is low speed, high drag, they don't get a good beating until I drive, thus the slightly darker color.

Discoloration from repeated heating and cooling cycles combined with exposure to oil.
Since plastic is more porous than metal it absorbs the color of the oil and oil vapors, leading it to appear "stained" or have a film on it.

Nothing to be concerned about.

Absolutely correct. The color of the underside is an opaque-ish white when the part is new. For whatever reason, Mobil ESP oils have a reddish tint when the oil is used. It doesn't "stain" the metal surfaces (as shown by the clean parts inside the camcase) like some Castrol oils are notorious for though. They be squeaky clean .