What does 15w-40 engine oil mean?

[AngelinaMarie]

Engine oil 15w-40 refers to the viscosity of the oil, indicating its applicable temperature range from -20 degrees Celsius to 40 degrees Celsius. Below is a detailed introduction to the types of engine oil models: 1. High-temperature type (such as SAE20-SAE50): The number represents the viscosity at 100*C, with higher numbers indicating higher viscosity. 2. Low-temperature type (such as SAEOW-SAE25W): W indicates it is only for winter use, with smaller numbers indicating lower viscosity and better low-temperature fluidity. 3. All-weather type (such as SAE15W/40, 10W/40, 5W/50): Indicates that the viscosity grade at low temperatures meets the requirements of SAE15W, 10W, and 5W respectively, and the viscosity grade at high temperatures meets the requirements of SAE40 and 50 respectively, belonging to the winter-summer universal type.