What does 15w-40 mean for engine oil?

[VanTalia]

W stands for WINTER. The number before W represents the freezing point temperature. The freezing point temperature corresponding to 15W engine oil is -20℃. The number after W represents the kinematic viscosity of the engine oil at 100℃. The higher the number, the higher the viscosity. 40 indicates that the kinematic viscosity standard at 100℃ is between 12.5mm and 16.3mm. The following is a related introduction about engine oil: 1. Engine oil is the lubricating oil used by the engine, composed of base oil and additives. The grade after the oil classification indicates its viscosity specification. The smaller the number before W, the better the low-temperature fluidity of the engine oil, indicating a lower usable ambient temperature and better protection for the engine during cold starts. 2. The number after W is an indicator of the oil's high-temperature resistance. The larger the number, the better the protection performance of the oil at high temperatures. Higher viscosity oil also has relatively higher resistance to the movement system, which not only consumes power and increases fuel consumption but also makes the oil more prone to oxidation, affecting protection during cold starts.

[JamesAnn]

The 15W-40 marking on engine oil actually refers to its viscosity grade. After years of using cars, I feel it acts like a protective film for the engine. The "W" in 15W stands for Winter, and the smaller number means it flows more easily at low temperatures, making winter starts easier. The 40 at the back indicates it maintains thickness at high temperatures, preventing parts from burning out when climbing hills in summer. This type of oil is particularly suitable for regions with distinct seasons, eliminating the hassle of changing oils. Choosing the wrong viscosity can make driving less smooth and may even increase fuel consumption, so always refer to your car's manual during maintenance to pick the right one.

[ValerieMarie]

When driving a friend's car, I noticed 15W-40 oil and asked a mechanic about it. He explained that the numbers indicate performance at different temperatures: 15W means good fluidity at low temperatures, quickly lubricating engine parts below zero for smoother cold starts. The 40 indicates moderate viscosity at high temperatures, preventing component wear. Using it in my family car, I found winter starts much easier, especially in northern regions. Don't underestimate these numbers - choosing the right oil extends engine life. Regularly check for oil degradation.

[DiKatherine]

15W-40 is a multi-grade motor oil specification. The first part, 15W, indicates low viscosity at cold temperatures, making it flow easily in cold weather; 40 represents high viscosity at high temperatures, providing better engine protection in hot conditions. I've used it during car repairs - this type of oil adapts to temperature changes and reduces wear. Choosing the wrong grade can lead to difficult starts or performance degradation.

[DeEleanor]

When buying engine oil, I saw 15W-40, and I looked it up—it's the viscosity grade. The 15W part is for low temperatures, with smaller numbers indicating better fluidity, suitable for cold regions; the 40 part indicates high high-temperature viscosity, offering good wear resistance. For daily driving, choosing the right one can save you trouble, otherwise, the engine might overheat. I usually decide whether to use it based on the ambient temperature.