What does 15w-40 engine oil mean?

[MacAdaline]

15w-40 engine oil represents the viscosity grade of the oil, with specific meanings as follows: 1. The number 15 indicates: The minimum temperature for winter use is -20°C. The smaller the number before the W, the lower the low-temperature viscosity, the better the low-temperature fluidity, and the lower the applicable minimum temperature. 2. The number 40 indicates: The high-temperature viscosity in summer. The larger the number after the W, the higher the applicable maximum temperature. Relevant information about engine oil is as follows: 1. Engine oil is the lubricant used by engines, composed of base oil and additives. 2. The density of engine oil is approximately 0.91×10³ (kg/m³). It can lubricate and reduce wear, assist in cooling, seal and prevent leaks, prevent rust and corrosion, and provide shock absorption and buffering for the engine. It is known as the 'blood' of the car.