Why Does Engine Oil Increase?
3 Answers
There are three reasons for the increase in engine oil: mixing of gasoline or water into the oil, engine component mechanisms, and temperature conditions. Below is an introduction to the causes of engine oil increase: 1. Mixing of gasoline or water into the oil: During vehicle operation, poor sealing of pistons or cylinders allows mixed gas to enter the crankcase. When the temperature drops, the gas condenses into liquid and flows back into the oil pan, increasing the oil level. At this time, water mixes into the oil. If fuel does not fully combust in the cylinders, it flows back into the oil pan, increasing the oil volume and diluting the oil, reducing its performance and failing to protect the engine. 2. Engine component mechanisms: The increase in oil volume is related to engine component mechanisms, such as insufficient cylinder pressure, poor cylinder sealing leading to reduced engine power and difficulty starting, or faulty fuel injectors causing dripping or excessive fuel injection. These two situations require monitoring by a mechanic to confirm the cause and perform repairs. 3. Temperature conditions: During cold starts, a richer fuel mixture is required, so the fuel injector sprays more gasoline. This results in excess gasoline flowing back into the oil pan. Generally, the main reason for oil increase is excessive fuel injection.
I've dealt with the issue of oil dilution before when repairing cars, which is usually caused by fuel mixing into the oil pan. Especially in vehicles with direct injection engines, unburned gasoline from the high-pressure fuel injection system can easily seep into the crankcase and mix with the engine oil, diluting it. Coolant leaks are also common, such as when aging gaskets allow antifreeze to enter and raise the oil level. Over time, the diluted oil loses its lubricating effectiveness, increasing wear on bearings or cylinder walls, and can even lead to engine seizure. I recommend checking the crankcase ventilation system and replacing damaged components immediately if you notice the oil level rising or detect a gasoline smell. It's also important to develop a habit of regularly checking the dipstick and avoiding frequent short trips that prevent the engine from fully warming up before shutting it off—this is especially crucial in cold climates. Some vehicles, like older Honda models, are indeed more prone to this issue due to design flaws, and timely replacement with higher viscosity oil can help mitigate damage.
My car started experiencing oil dilution last year, which really worried me at first. After researching, I learned the causes. The most common reason for rising oil levels is fuel leakage - in direct-injection turbocharged cars, unburned gasoline can mix with and dilute the engine oil during low-speed driving. Frequent short trips or shutting off the engine before proper warm-up worsens this issue, and cooling system failures may also introduce coolant. If ignored, diluted oil loses lubricity, accelerating component wear and shortening engine life. In my case, replacing the PCV valve helped. I recommend checking oil quality and viscosity during maintenance. Don't skip monthly dipstick inspections to monitor oil level changes - address any abnormalities immediately to avoid costly major repairs from neglected minor issues.
