How much can engine oil exceed the upper limit without causing issues?
2 Answers
Engine oil should not exceed the upper limit. If it does, the excess must be drained, and oil should be added according to the manual's requirements. Overfilling engine oil can lead to excessive internal pressure in the engine. The surplus oil may be forced into the combustion chamber under high pressure, resulting in incomplete combustion and the formation of large amounts of carbon deposits. Additionally, it increases internal engine resistance, causing poor acceleration. The functions of engine oil are: 1. To alleviate friction and high temperatures; 2. To reduce gas leakage and prevent contamination from external pollutants; 3. To prevent contact between water, air, acidic harmful gases, and engine components; 4. To cushion the rise in pressure at the engine cylinder ports; 5. To clean away dirt generated on the surfaces of engine components.
As a veteran driver with decades of experience, I've seen many cases of overfilled engine oil. Normally, the oil level should be between the upper and lower marks on the dipstick, but exceeding the upper limit by 2-3 millimeters usually isn't a major issue. This happened after my last oil change, and I drove 3,000 kilometers without any problems. However, remember to check the dipstick when the engine is cold, as hot engine measurements are inaccurate. If the oil level exceeds the limit by more than half a centimeter, be cautious—especially with German cars, as their engine seals are prone to leaks. During acceleration, the crankshaft can churn the oil and create bubbles, affecting lubrication. I recommend buying an oil extraction tool to remove some oil yourself or visiting a repair shop. Never ignore the issue.
