What does 15w-40 on engine oil mean?
2 Answers
In 15w-40 on engine oil, the 15 refers to the minimum operating temperature of -20 degrees Celsius, the w stands for winter, and the following 40 represents the high-temperature resistance index. Engine oil can be said to be the "blood" of a car, playing a crucial role in the operation of the vehicle. The performance of engine oil is as follows: 1. Lubricity: The ability of engine oil to reduce friction, slow down wear, and prevent metal sintering under various conditions is called the lubricity of the engine. 2. Low-temperature operability: The performance of engine oil to ensure easy starting and reliable oil supply in low-temperature conditions is called the low-temperature operability of engine oil. 3. Viscosity-temperature characteristics: The property of lubricating oil to change viscosity due to temperature changes is called viscosity-temperature characteristics.
The 15w-40 on engine oil indicates the viscosity grade, where W stands for Winter, reflecting its low-temperature performance. The number 15 refers to the low-temperature viscosity—the smaller the number, the smoother the cold start and the better it prevents freezing. The number 40 represents high-temperature viscosity—the larger the number, the better the high-temperature protection against wear. Having driven various vehicles, I find this grade suitable for all-season use across a wide temperature range, such as -15°C to 40°C, with reliable performance. However, to truly optimize performance, it's essential to match the oil type specified in the vehicle manual to the engine. Choosing the wrong oil may increase fuel consumption or shorten engine life. Generally, this grade works well for sedans and SUVs, but don’t just go for cheap brands without considering compatibility.
