What happens if you add too much engine oil?
4 Answers
Adding too much engine oil can cause the following harm to the engine: 1. Reduced power output and aging of crankshaft oil seals. Excessive oil increases the rotational resistance of the crankshaft, reducing the engine's power output and affecting the crankshaft oil seals. 2. Oil burning and emission failures. If there is too much oil, the engine components will churn vigorously during operation, which not only increases internal power loss but also increases the amount of oil splashed onto the cylinder walls, leading to oil burning failures. 3. Increased carbon deposits and higher fuel consumption. Oil may flow into the engine's combustion chamber, and prolonged oil burning can cause carbon buildup in the engine, increasing the amount of carbon deposits in the combustion chamber. When carbon deposits accumulate in the car, power decreases and fuel consumption rises. 4. Damage to the catalytic converter. As more oil enters the combustion chamber, exhaust emissions worsen, severely impacting the lifespan of the catalytic converter. 5. Accelerated wear of components. Accelerates wear on cylinders and pistons, thereby reducing the vehicle's lifespan.
I once made this mistake when changing my own oil. At the time, I noticed the dipstick reading was above the maximum mark but thought more oil would be safer. As a result, the engine sound became very muffled. After driving just a few kilometers, I saw blue smoke coming from the exhaust pipe and smelled a burnt odor, which scared me into shutting off the engine immediately. Later, the mechanic told me that overfilling the oil increases the resistance of the crankshaft's rotation, not only raising fuel consumption but also causing excessive internal pressure. This can lead to oil seals bursting and oil leaks, and in the worst cases, damage the catalytic converter. He helped me drain the excess oil—a full half-liter soda bottle's worth. Now, I always double-check the dipstick to ensure the oil level is right in the middle during every maintenance check.
From a professional perspective, the consequences of overfilling engine oil are quite severe. Firstly, the engine will experience reduced power output because the rotating components agitating excessive oil will consume power. Secondly, excessive oil pressure may damage the valve cover gasket – my old Jeep once developed oil pan leakage due to this. Even worse, surplus oil can be drawn into the combustion chamber through the crankcase ventilation system, not only causing carbon buildup but also contaminating spark plugs. I recommend addressing overfill immediately. If the level doesn't exceed the maximum mark by more than half a centimeter, you can check the dipstick after warming up the engine and waiting ten minutes after shutdown – natural settling will lower the level somewhat. For significant overfill, it's best to use a specialized pump to extract the excess.
My neighbor Lao Wang is a living example. He always complained about the short maintenance intervals and insisted on overfilling the engine oil. As a result, last year he spent eight thousand on a major engine overhaul. The mechanic found the piston rings stuck with carbon deposits, all caused by excessive oil entering the combustion chamber. The oil pan sealant was completely blown out by the high pressure, and the crankshaft oil seal leaked like a sieve. Now Lao Wang has learned his lesson. After every maintenance, he asks me to help check the dipstick. I taught him the correct method: when the engine is cold, wipe the dipstick clean, insert it all the way, and the ideal oil level should be at two-thirds between the upper and lower marks.
