What does the engine oil grade 5w-40 mean?
2 Answers
The engine oil grade 5w-40 means that W stands for WINTER, indicating it is suitable for winter use. The number 5 before W represents the viscosity at low temperatures. The smaller the number, the better the fluidity at low temperatures and the stronger the cold resistance. The number 40 refers to the viscosity at 100°C. The larger the number, the higher the viscosity and the stronger the high-temperature resistance. The specific introduction of engine oil grades for cars is as follows: 1. Winter oil grades: The winter oil grades are: 0W, 5W, 10W, 15W, 20W, 25W. The symbol W stands for WINTER, and the smaller the number before W, the lower the low-temperature viscosity, the better the low-temperature fluidity, and the lower the applicable minimum temperature. 2. All-season oil grades: The all-season oil grades are: 5W-20, 5W-30, 5W-40, 5W-50, 10W-20, 10W-30, 10W-40, 10W-50, 15W-20, 15W-30, 15W-40, 15W-50, 20W-20, 20W-30, 20W-40, 20W-50. The smaller the number representing the winter part, and the larger the number representing the summer part, the higher the viscosity and the wider the applicable temperature range.
I've driven in various weather conditions and road types, and learned that the 5W-40 oil grade is crucial—it represents two viscosity ratings. The '5' part indicates cold-start performance; a lower number means the oil flows more easily at low temperatures, quickly protecting the engine. The '40' part refers to the viscosity at high temperatures; a higher number ensures the oil maintains sufficient thickness to lubricate components and reduce wear. This design makes the oil suitable for all seasons—smooth engine starts in winter without harming the engine, and effective protection without thinning out in summer heat. I currently use this grade, and my car starts without any hesitation. When choosing oil, always check your car's manual recommendations; otherwise, you might face higher fuel consumption or reduced engine lifespan. Also, consider local climate—regions with large temperature swings benefit more, avoiding frequent seasonal oil changes. My personal experience confirms it balances protection and fluidity, making it particularly hassle-free.
