What does the engine oil grade 10w40 mean?
1 Answers
The number 10 represents the minimum applicable temperature of the oil at -25 degrees Celsius, W stands for Winter, and 40 indicates the high-temperature viscosity of the oil, which is the meaning of 10w40 engine oil. The oil grade typically denotes viscosity and quality. The oil grade consists of two parts: classification and viscosity specification, with specific interpretations as follows: w represents the cold-start performance, and the smaller the number before w, the easier it is to start the engine in cold weather. Common grades include 0w, 5w, 10w, and 15w. The number 40 indicates the viscosity characteristics of the oil at high temperatures. High-viscosity oils (with higher values) may be more suitable for high-speed driving or heavy-duty vehicles. The number after w 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 grade following the oil classification represents its viscosity specification. For example, in "15w-40, 5w-40," the lower the number before w, the better the engine protection during cold starts. For instance, 5w represents resistance to external temperatures as low as -30°C, while 20w can withstand temperatures as low as -15°C. The number after w represents the oil's kinematic viscosity at 100°C, with higher numbers indicating higher viscosity. The viscosity of lubricating oils is often labeled using the SAE grade, where SAE stands for the "Society of Automotive Engineers." Internationally, the SAE (Society of Automotive Engineers) viscosity grade and API (American Petroleum Institute) quality grade are widely adopted. When selecting engine oil, consider the following precautions: Choose oil based on the engine's requirements. It is unnecessary to use overly advanced oil in engines with lower requirements, nor should lower-grade oil be used in engines with higher requirements. Multi-grade oils are preferred because they are economical, long-lasting, and efficient, providing better protection for the engine. Due to the characteristics of multi-grade oils, they may appear darker prematurely and have lower oil pressure compared to conventional oils during use, which is normal.
