What does 0w40 mean?

[GrahamLynn]

In 0w40, the W stands for Winter. The smaller the number before it, the better the low-temperature fluidity of the oil, indicating a lower usable ambient temperature and better engine protection during cold starts. The number 40 indicates that the kinematic viscosity standard at 100°C is between 12.5m㎡/s and 16.3m㎡/s. Here is some related information: The viscosity of lubricating oil is often identified using SAE grades, where SAE is the abbreviation for the "Society of Automotive Engineers." The number after the "W" (after the hyphen) is an indicator of the oil's high-temperature resistance. The larger the number, the better the oil's protective performance at high temperatures. The selection of oil viscosity should meet both low-temperature startability and high-temperature lubricity. Choose viscosity grades based on region, season, and temperature, and try to use multi-grade oils. In extremely cold regions during winter, engine oils such as 0W, 5W, or 0W/20 or 5W/20 multi-grade oils should be used; in hot regions during summer, 40-grade oil or 20W/40 oils should be used.