What are the consequences of excessive engine oil?

[ArcherLynn]

Excessive engine oil can lead to reduced vehicle power and oil leakage issues, cause oil burning, and result in clogging of the three-way catalytic converter. Reduced power and oil leakage issues: Too much oil increases internal oil pressure, causing poor operation of some engine components, which fails to provide sufficient power to the vehicle. Additionally, the increased oil pressure may damage seals, leading to oil leaks. Oil burning situation: When the engine oil exceeds the standard level, the crankshaft's rotation will churn the oil, producing a large number of bubbles. These bubbles are carried into the combustion chamber through the ventilation system and burned, resulting in oil burning. These bubbles can also cause wear on the cylinders and pistons. Three-way catalytic converter clogging: Burning engine oil produces certain residues that are not expelled from the vehicle but instead accumulate inside the three-way catalytic converter. Since this is not easily noticeable during normal operation, by the time it accumulates to a certain extent, the three-way catalytic converter may be beyond repair.

[MacBentley]

Last time, my friend's car repair experience left a deep impression on me. His car had too much engine oil added, which made the engine run with great difficulty. The car obviously lacked power when driving and felt particularly sluggish during acceleration. If the engine oil level exceeds the standard, the pressure in the crankcase will skyrocket, causing the oil seals and gaskets to fail, and oil stains begin to seep out. Over time, the entire engine compartment becomes dirty. The most troublesome part is that the excess oil gets whipped into foam by the crankshaft, significantly reducing the lubrication effect, leading to premature wear of piston rings and cylinder walls. He also noticed an unexplained increase in fuel consumption, blue smoke from the exhaust pipe, and even the catalytic converter got clogged by the residue of burning oil. In the end, he spent over 4,000 yuan replacing parts to fix it. He really should have drained the excess oil beforehand.

[EmmanuelFitz]

I've seen quite a few cars with problems caused by overfilled engine oil at 4S shops. This is no trivial matter. When the oil level is too high in the engine, the crankshaft rotation will agitate the oil and create foam. This aerated oil provides significantly poorer lubrication, causing critical components to wear out rapidly. Moreover, excessive pressure can easily damage seals, often leading to oil leaks at the oil pan and crankshaft seals. If oil leaks onto the exhaust pipe, there's even a fire risk. Owners may notice heavier throttle response, weaker power output, and fuel consumption increasing by 1-2 liters more than usual. The most troublesome issue occurs when oil enters the combustion chamber - this leads to severe carbon buildup, often destroying the catalytic converter. Replacing a catalytic converter can cost several thousand yuan. I'd like to remind everyone not to overfill when changing engine oil.

[EvangelineDella]

I have a deep understanding of the issue of overfilling engine oil. After the last maintenance on my used car, the oil level exceeded the upper limit. While driving, I clearly noticed the engine sound became muffled, and the acceleration was sluggish when stepping on the gas pedal. The mechanic said excess oil could be drawn into the combustion chamber by the crankshaft, causing blue smoke from the exhaust pipe with a burnt smell. Over time, the piston rings could seize, and the cylinder walls could get scratched, making it impossible to pass the emissions test. I also noticed foam on the dipstick, which the mechanic explained has poor lubricity and can easily cause bearing wear. After removing half a liter of oil, the abnormal noise disappeared. I recommend checking the dipstick when the engine is cold, with the oil level ideally in the middle of the scale.