What does 10w40 mean?
2 Answers
10w40 has the following meanings: 1. 10 represents the minimum applicable temperature of the oil, which is -25°C. 2. W stands for Winter. 3. 40 represents the high-temperature viscosity of the oil, with a kinematic viscosity of 14.5cst at 100°C. 4. The W in the grade indicates Winter, and the preceding number represents the oil's low-temperature fluidity—the smaller the number, the better the low-temperature fluidity. The number after W represents the oil viscosity grade at 100°C—the larger the number, the better the protection the oil provides to the engine at high temperatures.
10w40 is the viscosity grade of engine oil, indicating its flow characteristics at different temperatures. The 'W' before the first number 10 stands for Winter, and 10 refers to the oil's viscosity in cold weather (around -25°C) — the lower the number, the easier cold starts are, allowing the engine to lubricate quickly. The 40 represents the viscosity at high temperatures (around 100°C), where a higher number means thicker oil, better protecting engine components from wear in hot conditions. It's like the thickness of clothing: too thin and you're cold in winter, too thick and you're stuffy in summer. Choosing the right 10w40 is crucial because using the wrong oil can make starting difficult, increase fuel consumption, or cause premature engine damage. I often help friends check their oil, recommending they follow the car manual's guidelines and consider local climate. For example, in Beijing winters, a lower 'W' oil is better, while in hot Hainan, a higher number is ideal. Regular oil changes every 5,000 km or so keep the engine healthy and extend its lifespan.
