What does 10w40 mean for car engine oil?
2 Answers
Car engine oil 10w40 refers to the viscosity grade of the oil. The number 10 indicates the minimum applicable temperature of the oil is -25 degrees Celsius, W stands for all-season use (both summer and winter), and 40 represents the high-temperature viscosity of the oil. The higher this number, the thicker the oil is at high temperatures. W stands for winter, and 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 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 oil I've been using in my car is 10w40, which actually represents the viscosity characteristics of the oil. The W stands for winter, and the number 10 before it indicates low-temperature fluidity. During cold starts in winter, the oil won't be too thick and can still flow normally at around -25 degrees Celsius. The 40 after it represents high-temperature viscosity. At the engine's operating temperature of 100 degrees, it has higher viscosity and can form a sufficiently thick oil film to protect the engine. This type of oil can be used all year round and is especially suitable for ordinary family cars and regions with significant temperature variations. When choosing oil, you should refer to the vehicle's manual. Older cars with larger engine gaps are better suited for higher viscosity oil, while newer cars should use lower viscosity oil for better fuel efficiency. Remember to change the oil on time; otherwise, even the best viscosity rating won't help.
