Does engine oil become thinner or thicker with use?

[VanSimon]

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.

[McGabriela]

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.

[Clay]

Engine oil tends to become thinner over time with use, which is a common phenomenon primarily due to high temperatures and contamination during operation. When handling vehicle maintenance, I often inspect used oil samples, and viscosity measurements consistently show significantly lower values compared to fresh oil. This is mainly because the heat generated by engine operation causes oxidation and breakdown of oil molecules, while contaminants like dust or moisture further dilute the oil's consistency. Thinner oil leads to reduced lubricating performance, potentially accelerating component wear and even causing overheating issues. However, this isn't absolute - if excessive low-quality additives are mixed into the oil, it may occasionally feel thicker, but overall thinning remains predominant. I recommend checking oil condition by rubbing used oil samples between fingers to clearly detect thinning, and adhering to scheduled oil changes to prevent problems. Selecting the correct viscosity grade (e.g., 5W-30) matching your vehicle model is crucial to avoid minor engine issues accumulating into major troubles.

[DeAriana]

Engine oil tends to thin out over time due to daily engine operation. I've noticed this while driving - fresh oil is thick when poured in, but after a few months of use, checking the dipstick reveals significantly thinner oil. The reason is simple: high engine temperatures cause oil breakdown, and combined with air and dust contamination, viscosity decreases. Thinner oil leads to slightly louder engine noise and less stable acceleration. That's why I now change my oil every 5,000 kilometers to maintain smooth vehicle operation. Neglecting this could eventually cause engine damage, which isn't worth the risk. Choosing a reliable brand of engine oil can help it last longer.

[McLila]

Engine oil tends to thin out rather than thicken during use, primarily due to thermal oxidation and contamination leading to viscosity reduction. Oxidation breaks down oil molecules under high temperatures, while impurities like metal particles or moisture dilute the oil, compromising lubrication efficiency. Thinned oil increases engine wear risks and may shorten component lifespan. I recommend using viscosity testers or monitoring dipstick changes to track oil condition, ensuring timely replacement. High-quality oils with stabilizing additives can slow this process, but regular maintenance remains crucial to prevent minor oversights from causing major failures. Choosing the right SAE grade oil (e.g., 0W-40) enhances protection and maintains optimal engine performance.

[VanEmily]

Engine oil tends to thin out during vehicle operation in most cases—this isn't speculation but experience-based. Exposed to high engine temperatures, oil oxidizes and breaks down, gradually losing viscosity while contaminants mix in, making it thinner. The consequence is insufficient lubrication, increased engine friction, and noticeably louder noise. I've tested different oils: synthetic oils last longer before thinning. Avoid misconceptions: don't assume oil thickens unless excessively contaminated. Regular oil changes (e.g., twice a year) with quality products protect the engine and extend vehicle lifespan. Monitor dipstick color changes routinely to address issues early and reduce repair costs.