Why does engine oil turn black so quickly?
2 Answers
Engine oil turns black in a short time due to the action of detergents and dispersants, and the oxidation of the oil. Specific explanations are as follows: Due to the oxidation of engine oil in use: If the engine oil becomes viscous and produces acidic byproducts after some use, it should be replaced promptly. Otherwise, it may damage engine components and affect normal engine operation. Due to the function of detergents and dispersants: Currently, engine oil generally contains detergents and dispersants that absorb carbon deposits from combustion and oxides from the oil to ensure the cleanliness of the engine interior. Therefore, newly replaced oil turning black is not necessarily caused by a dirty engine interior. As long as the oil is changed according to the specified intervals, it should be fine.
I've been driving cars for over a decade and often notice that new engine oil turns black after just a few hundred kilometers. This happens because the engine leaves behind carbon particles and impurities when burning gasoline, and the oil's job is to encapsulate them to prevent damage to engine components. Especially during frequent stop-and-go city traffic or short trips where combustion is incomplete, carbon buildup occurs more easily, causing the oil to darken faster. This is actually quite normal—it shows the oil's detergents are working, not that the oil quality is poor or the engine has issues. I recommend sticking to the oil change intervals without delay, typically every 5,000 to 10,000 kilometers based on driving habits. Changing it too often is wasteful, but regular maintenance ensures the engine runs longer and smoother. Highway driving at steady speeds keeps the oil cleaner slightly longer, so don't be alarmed by the dark color.
