What is the reason for the oil in the intake pipe?

The reasons for oil in the intake pipe are: 1, and the engine has been idling for a long time; 2. The air conditioner filter element is dirty; 3. Crankcase ventilation system is blocked or deformed; 4. The oil inlet and return pipes of turbocharger are blocked, leaked or deformed; 5. The lubricating oil of the turbocharger intermediate shell is coking; 6, cylinder wear leads to piston ring blowby; 7. The flow resistance in the exhaust system is too large. The function of engine oil: 1, which makes the piston and cylinder slide, and the spindle and bearing bush slide to prevent parts from being worn; 2. Auxiliary cooling; 3. Remove carbide and sludge from engine parts; 4, sealed and leak-proof; 5. Rust prevention and corrosion protection; 6. Shock absorption and buffering; 7. Wear resistance.