What does 10w40 engine oil mean?
2 Answers
10w40 engine oil refers to an oil with a kinematic viscosity of 14.5cst at 100°C. The '10' indicates that the oil is suitable for low temperatures down to -25°C, 'w' stands for winter, and '40' represents the high-temperature viscosity of the oil. The number before 'w' indicates the oil's low-temperature fluidity—the smaller the number, the better the fluidity at low temperatures. The number after 'w' represents the oil's viscosity grade at 100°C—the higher the number, the better the protection the oil provides to the engine at high temperatures. Lubricating oil must have sufficient viscosity to prevent wear between moving parts and to form an oil film between them at various operating temperatures. Higher viscosity is not always better; the choice of oil should be based on the temperature range during use, and a lower viscosity oil should be selected whenever possible.
I've been driving and repairing cars for years, and 10w40 oil refers to the viscosity grade of engine oil. That string of numbers is particularly practical. The first number, 10, represents the viscosity during cold starts. The lower this number, the more suitable it is for winter low temperatures, as the oil flows faster when starting the car, protecting the engine. The 'W' stands for winter, and 40 is the viscosity at high temperatures. When driving at high speeds or in hot summers, the oil film is thicker, preventing wear. I choose 10w40 because it suits most everyday sedans, especially in temperate climates like China. Many of my customers use it, and it works well for regular family cars or medium-performance vehicles. Of course, always check the owner's manual—don't use it randomly. For example, older cars might be better suited to different grades. When changing oil, I recommend regular checks. Don't wait until the warning light comes on, as it can affect engine lifespan. Remember, oil quality is also important. Pair it with a good filter, and you'll be much safer after a few thousand kilometers.
