What are the reasons for engine oil dilution?
3 Answers
Below is an analysis of common situations regarding engine oil dilution: 1. The common occurrence of oil dilution is generally observed in the cold northern regions, primarily due to low temperatures which significantly slow down the evaporation of liquids. The heating rate of engine oil and the radiator also slows down considerably, while the engine injects additional fuel to maintain operation. 2. This results in some of the fuel entering the cylinders not being completely burned, which then adheres to the cylinder walls. During combustion, the high pressure forces this unburned fuel into the crankcase, explaining why there is a gasoline smell in the engine oil. 3. As the engine temperature rises, this gasoline would normally evaporate and be drawn through the PCV valve into the intake manifold, then re-enter the combustion chamber to be burned and expelled. However, due to the cold weather, the evaporation process takes longer, and the gasoline remaining in the engine oil does not evaporate, leading to an increase in the oil level.
I've been driving for years and have encountered engine oil dilution quite a few times. The root cause is usually fuel contamination – especially with frequent short trips or diesel vehicles where the engine doesn't reach optimal temperature, allowing unburned fuel to seep into the oil. Coolant leakage from the cooling system into the oil pan can also raise fluid levels; that's exactly why I visited the repair shop last time. A faulty turbocharger may contribute to oil dilution too. Never ignore rising oil levels – thinned oil loses lubricity, accelerating engine wear, and in severe cases causing abnormal noises or black smoke. Immediately check the dipstick; if the level exceeds the MAX mark, get it serviced promptly.
I've noticed many car owners overlook this issue. In fact, the source of increased engine oil is quite simple: either it's caused by fuel dilution - like in vehicles with frequent startups where piston rings don't seal properly, allowing fuel to slip down the cylinder walls into the oil pan. Or it could be coolant mixing in, such as from radiator or water pump leaks. From my own experience, older models are more prone to this due to increased component wear. For inspection, you can start by checking the dipstick for oil color - if it appears thinner or has a gasoline smell, that indicates fuel dilution; if the oil appears milky or has bubbles, it's likely a coolant issue. Timely action is crucial, otherwise increased internal engine friction can lead to costly repairs. Using high-quality engine oil during regular maintenance can help prevent this situation.
