What are the reasons for oil in the intake manifold?

1 Answers
RobertMarie
07/24/25 6:28pm
The reasons for oil in the intake manifold are: 1. Prolonged engine idling; 2. Dirty air filter; 3. Clogged or deformed crankcase ventilation system; 4. Clogged, leaking, or deformed turbocharger oil inlet/return pipes; 5. Coking of lubricating oil in the turbocharger's intermediate housing; 6. Cylinder wear causing piston ring blow-by; 7. Excessive flow resistance in the exhaust system. Modern engines are equipped with an Exhaust Gas Recirculation (EGR) system, primarily designed to reduce the levels of hydrocarbons and nitrogen oxides in the exhaust. Its working principle is to redirect a small portion of exhaust gases to the intake manifold during high-load and high-speed engine operation, where they mix with fuel vapor to participate in combustion, absorbing heat generated during combustion and controlling temperature to suppress the formation of nitrogen oxides.
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