Does engine oil become thinner or thicker with use?
2 Answers
As the usage time increases, engine oil will become increasingly thicker. The reasons for engine oil thickening are as follows: 1. Changes in viscosity index improvers: Most engine oils contain viscosity index improvers. Under prolonged operation, these additives can be sheared and lose their original viscosity, causing the oil's viscosity to decrease to some extent. 2. Oxidation: The oil undergoes oxidation in the engine, leading to thickening. 3. Other contaminants: During operation in the engine, a significant amount of sludge and other impurities are generated, which are dispersed in the oil by detergents and dispersants, resulting in increased viscosity.
Engine oil typically becomes thinner during actual use, primarily due to oxidation and breakdown caused by high engine operating temperatures. When oil is continuously exposed to high heat, its viscosity decreases, making it flow more smoothly. I've driven several cars, and every time I went for an oil change after a few thousand kilometers, the old oil was always thinner than the new oil and darker in color. This is because thermal decomposition causes it to lose its original viscous properties. Thinner oil provides poorer lubrication, increases engine noise, and can even lead to higher fuel consumption. For example, the last time I neglected the oil change interval, my engine made strange noises upon startup, and it took a lot of effort to fix. That's why it's important to develop a regular maintenance habit and not wait until problems arise. The oil change frequency should follow the manual's recommendation, usually every 5,000 to 10,000 kilometers. Using high-quality synthetic oil can also slow down this process and extend engine life.
