How to Determine the Quality of Engine Oil?
2 Answers
You can determine the quality level of engine oil from the specifications on the oil packaging. Taking "0W-40 API SN/CF" as an example, the first part "0W40" is the main grade. The smaller the number before the "W," the better the low-temperature fluidity, which provides better engine protection. "0W" indicates that the oil can be used at temperatures as low as -35°C. The number "40" after the "W" represents the viscosity index of the oil at high temperatures. The higher the number, the higher the viscosity, which also means better engine protection. Here are methods to determine the quality of engine oil: 1. Listen to the engine sound after adding oil: If, after driving a few hundred kilometers, the engine sound becomes smoother and quieter, and the vibration stabilizes, it indicates good oil quality. Conversely, if the engine sound becomes louder, duller, or the vibration increases, the oil may be problematic. 2. Observe the color and smell of the oil: High-quality oil is light in color, transparent, free of impurities, suspended particles, or sediment, and flows well when shaken. The more transparent the oil, the higher its quality. Fake oil often has a pungent smell due to inferior raw materials or processes, while genuine oil does not. 3. Observe in low temperatures: Since engine oils vary in low-temperature performance, seal a small bottle of oil and place it in a freezer set to -18°C. After 6 hours, check its fluidity. High-quality oil will flow noticeably better, indicating better engine protection in cold conditions. 4. Shake and observe: Pour the oil into a bottle and shake it vigorously until many bubbles form. Then observe how quickly the bubbles disappear. Higher-grade, better-quality oil will see bubbles dissipate faster. If bubbles persist, the oil may be problematic. 5. Check fuel consumption after adding oil: Qualified oil, due to its superior lubrication, anti-wear, and cleaning properties, reduces friction in engine components, leading to better fuel efficiency. If fuel consumption increases significantly after adding new oil, the oil may be of poor quality.
I've been working with cars for decades, and judging the quality of engine oil requires a combination of methods. First, check the color by pulling out the dipstick—fresh oil is usually a clear amber-yellow, but if it turns dark black or cloudy, it indicates oxidation and contamination, meaning it's time for a change. The smell test is crucial: fresh oil has little to no odor, while degraded oil may carry a gasoline or burnt smell, signaling engine combustion issues. The simplest viscosity test is by hand: drip a bit of oil between your fingers and rub them together. If it feels thin like water or lacks stickiness, it means the oil has degraded and lost its lubricating properties. I also recommend using oil test strips—place a drop on the strip, and if it spreads to form a clear ring, the oil is still good; a blurry or heavily spread pattern indicates severe contamination and the need for replacement. Mileage and time are key: conventional mineral oil should be changed every 5,000 to 8,000 kilometers, while synthetic oil can last up to 12,000 kilometers. However, if you frequently drive in high-temperature areas or take many short trips, the oil degrades faster. Engine performance also gives signals: sudden increases in noise, rough starts, or noticeably higher fuel consumption may all point to degraded oil. Regular checks and maintenance ensure your engine runs smoothly for years to come.