Skoda's cutting-edge throttle pipe has oil. Why is it so dark?

Skoda's cutting-edge throttle pipe has engine oil, which is particularly dark because of the pressure relationship when the engine is running, and some combustible mixture will run in from the gap between the cylinder and the piston ring. If it is not discharged in time, the internal pressure of the engine will be too high, so every engine has a crankcase ventilation valve, and the excess combustible mixture will be discharged from the exhaust valve and returned to the intake manifold to participate in engine combustion.

Throttle function:

This is a controllable valve, which is used to control air to enter the engine. After entering the intake pipe, it is mixed with gasoline to form combustible mixture, which participates in combustion and does work. Throttle is an important part of EFI automobile engine system. Its upper part is the air filter, and the lower part is the engine body, which is the throat of the automobile engine. Whether the vehicle accelerates flexibly or not has a great relationship with the cleanliness of the throttle.