What does 10w40 engine oil mean?
2 Answers
10w40 engine oil is suitable for environments above minus 25 degrees Celsius. The '10' represents the minimum applicable temperature of the oil, which is minus 25 degrees, 'w' stands for Winter, and '40' represents the high-temperature viscosity of the oil. The kinematic viscosity of engine oil at 100 degrees Celsius is 14.5 centistokes. The number before 'w' indicates the low-temperature fluidity of the oil; the smaller the number, the better the low-temperature fluidity. The number after 'w' represents the viscosity grade of the oil at 100 degrees Celsius; the larger this number, the better the protection the oil provides to the engine at high temperatures. Engine oil must have sufficient viscosity to prevent wear between moving parts and to form an oil film between them under various operating temperatures. However, the fluidity of the oil should not be so high as to affect engine startup; it must generate the least friction under continuous operating conditions.
10w40 oil refers to the viscosity grade of the oil. The 10w part indicates the winter viscosity, where a smaller number means better fluidity in cold weather, making it easier to start the engine, such as at around -25°C. The 40 is the high-temperature viscosity, where a larger number indicates thicker oil when the engine heats up, protecting metal parts from wear. This type of oil is suitable for areas with large seasonal temperature variations. I use it year-round in my car and feel the engine runs smoothly. It is more durable than thinner oils like 5w30, especially suitable for older cars or high-load driving. When choosing, confirm the SAE standard and API certification to ensure quality, and it is recommended to change it every 5,000 to 10,000 kilometers to avoid oil degradation. Remember not to use the wrong viscosity, as it can easily increase fuel consumption or damage the engine. Check the oil level during cold starts in winter for a more secure drive.
