Does adding too much engine oil have any impact?
4 Answers
Adding too much engine oil does have an impact, specifically: 1. Increased fuel consumption; 2. During engine operation, various components will experience intense agitation, increasing internal power loss; 3. Increased resistance on the crankshaft, affecting power output; 4. Worsened exhaust emissions, which in severe cases may cause the three-way catalytic converter to become poisoned and damaged. 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. Engine oil consists of two parts: base oil and additives. The base oil is the main component of the lubricant, determining its basic properties, while additives compensate for and improve the shortcomings of the base oil, imparting certain new properties, making them an important part of the lubricant.
Last time I got my car serviced, I overfilled the engine oil by half a liter and jokingly said more lubrication is better. But after just three days of driving, problems emerged. When I stepped on the gas, the car felt like it was dragging a block of iron, struggling to accelerate. A friend sitting in the back even smelled engine oil. The mechanic explained that excess oil gets whipped by the crankshaft, creating bubbles. These foam bubbles then enter the lubrication system through the oil pump, causing hydraulic lifters to tick. The worst part is that when pistons move downward, the oil rings can't properly scrape off the excess oil. This not only leads to oil burning (blue smoke) but can also clog the catalytic converter. The mechanic emphasized that the oil fill line isn't just for show - if it's overfilled by even 1cm above the max mark, you need to drain it. The easiest method is using a syringe with tubing inserted through the dipstick tube to extract the excess oil.
I've seen many car owners believe that adding more engine oil is safer, but in fact, the consequences can be quite serious. When the oil level is too high, the high-speed rotating crankshaft will repeatedly churn the oil in the oil pan, much like a whisk beating cream, creating a large amount of foam. These bubbles entering the lubrication passages can cause oil starvation at bearing positions, leading to damage. I've noticed that some engines may also leak oil from the oil seal positions, as the rubber seals can deform and fail under continuous high-pressure oil impact. It's recommended to check the dipstick when the engine is cold after maintenance, with the oil level ideally at the 3/4 mark between the upper and lower limits. For DIY solutions, you can use a modified dish soap bottle as an oil extraction tool to remove excess oil in just ten minutes.
When engine oil exceeds the upper limit of the dipstick: 1. The resistance of the crankshaft stirring oil increases, leading to a fuel consumption rise of approximately 5%; 2. Foamy oil causes abnormal noise in the hydraulic lifters; 3. Oil entering the combustion chamber may clog the three-way catalytic converter; 4. Excessive crankcase pressure can damage the valve cover gasket. Recently handled a Nissan Sylphy case where post-maintenance fuel consumption surged from 7L to 9L. Removing 300ml of excess oil immediately restored normal levels. Teach everyone self-check: Park on level ground, turn off the engine for 10 minutes, pull out the dipstick, wipe it clean, reinsert it, and the oil level should be within the grid area. If exceeded, use a shampoo pump head connected to an infusion tube inserted into the dipstick tube to extract oil.
