Does adding too much engine oil affect the car?

[StMatthew]

Adding too much engine oil does have an impact on the car. The specific effects include: Increased fuel consumption; increased power loss inside the engine; reduced power output; in severe cases, it may cause poisoning and damage to the catalytic converter. Composition of engine oil: Engine oil consists of base oil and additives. The base oil is the main component of lubricating oil, determining its basic properties, while additives compensate for and improve the shortcomings of the base oil, making them an essential part of lubricating oil. Engine oil, also known as engine lubricant, serves to lubricate and reduce friction, assist in cooling, seal against leaks, prevent rust and corrosion, and provide shock absorption for the engine.

[SanEvan]

Once when I was traveling out of town, I noticed my car had no power and was guzzling fuel. After pulling over and checking the dipstick, I found the oil level was way above the max mark! The mechanic said it's like trying to run in a heavy winter coat – the excess oil gets churned by the rotating components, creating foam. That aerated oil causes the oil pump to suck in air bubbles, leaving metal parts inadequately lubricated. The scariest part? Oil seals can burst from overpressure, suddenly dumping black oil on the road – extremely dangerous. The mechanic used a syringe with tubing to extract half a liter through the dipstick tube, and the car immediately ran smoother. Moral: Always check oil levels when the engine is cold, ensuring it's between the min and max marks for safety.

[Weston]

After the last maintenance, I felt the steering wheel was unusually heavy when driving on the highway. My best friend reminded me to check the engine oil, and when I pulled out the dipstick, it was completely covered in oil stains. The mechanic told me that excess oil can cause a surge in crankcase pressure. When the pressure gets too high, the oil-gas separator can fail, with the most obvious sign being blue smoke from the exhaust pipe when starting the car. My car now needs a liter of oil every 5,000 kilometers because the piston rings were damaged from overfilling. It's recommended to add engine oil in three small batches, waiting five minutes between each addition to let the oil settle before measuring—this method is the most accurate.

[JoannaFitz]

We always discuss this during lunch breaks at our car factory. Even if the engine oil exceeds the marked line by just half a centimeter, the crankshaft rotation resistance can increase by 15%, and fuel consumption spikes immediately. Once, after disassembling an engine, we found concave marks on the connecting rod bearings caused by foamy oil—this kind of damage is irreversible. A colleague’s SUV had it worse—an extra liter of oil directly ruined the rear crankshaft oil seal. Now, we all use graduated jugs to add oil. After filling, we must run the engine for three minutes, then turn it off and wait ten minutes for a recheck—this ensures the most accurate measurement.

[CalvinAnn]

The mechanic demonstrates with the oil extraction tube: Excess oil will be violently whipped by the crankshaft arms, turning into foam that mixes into the combustion chamber. When the piston rings get coated with this foamy oil, they lose elasticity, leading to oil burning. The most extreme case we've handled was a customer who added eight liters of oil (only 4.5L needed). Three days later, the catalytic converter was completely clogged. The DIY fix is simple: Buy a large syringe from the pharmacy, attach an infusion tube, and slowly extract the excess oil through the dipstick hole until it reaches the middle mark.

[LeMorgan]

Last year before a long-distance trip, I got an oil change, but the mechanic accidentally overfilled it by half a liter. At first, it just resulted in higher fuel consumption, but then suddenly the engine warning light came on while driving. I pulled over immediately to check and found oil leaking from the oil cap, with white smoke billowing from the entire engine bay. The repair shop said the excess oil had damaged the crankcase ventilation valve, causing high-pressure exhaust gases to spray oil everywhere, and the cleanup cost me 800 yuan. Now, every time I get an oil change, I watch the mechanic closely: first add 90% of the amount specified in the manual, wait ten minutes, then check the dipstick and top up if needed. This way, there’s no chance of a mistake.