What is the reason for engine oil burning when the car's exhaust valve is broken?
2 Answers
Car exhaust valve failure leading to engine oil burning is caused by: 1. Faulty design in the crankcase forced ventilation system; 2. Mesh patterns on the cylinder walls. Hazards of engine oil burning in cars: Generates large amounts of carbon deposits and gum, resulting in increased fuel consumption and insufficient power in the engine, while potentially causing difficulty in starting the engine and leading to severe engine wear. The functions of engine oil are: 1. To alleviate friction and high temperatures; 2. To reduce gas leakage and prevent external pollutants; 3. To prevent contact between water, air, acidic harmful gases, and components; 4. To cushion the rise in pressure at the engine cylinder port; 5. To flush away dirt produced on the working surfaces of components.
A faulty PCV (Positive Crankcase Ventilation) valve can cause oil burning primarily because it regulates crankcase pressure. Normally, this valve adjusts the internal pressure of the crankcase, allowing the oil-gas mixture to flow back into the intake manifold for combustion. If it fails—such as becoming clogged or stuck—the crankcase pressure becomes uncontrolled. High pressure may force oil and gases out, while low pressure can create a vacuum that draws oil away. As a result, oil is sucked into the combustion chamber and burned, leading to blue smoke from the exhaust and accelerated oil consumption. Over time, this can increase carbon buildup inside the engine, affecting spark plugs and valves, and potentially damaging the catalytic converter. Vehicle maintenance also plays a role—dusty environments or delayed oil changes accelerate valve wear and failure. It's recommended to inspect the PCV valve annually and replace it promptly to prevent cascading issues. If oil burning occurs, don't ignore it—repair it immediately for safety.
