What is the difference between 10w-40 and 5w-40?

[LeRylee]

10w-40 and 5w-40 mainly have the following differences: 1. Both 5w-40 and 10w-40 are oil viscosity grades. The letter W stands for Winter, and in fact, oils with the W letter are all-season oils suitable for both winter and summer. 2. The number 40 represents the high-temperature viscosity grade of the oil. The larger the number, the stronger the high-temperature viscosity of the oil, the thicker the oil film, and the better the sealing and protective capabilities. 3. The numbers 5 and 10 represent the minimum applicable temperature of the oil, or its low-temperature fluidity. 10 indicates that the minimum applicable temperature of the oil is -25 degrees Celsius, while 5 indicates that the minimum applicable temperature of the oil is -30 degrees Celsius.

[DelCameron]

I've been driving cars for many years and found that oil viscosity is quite crucial. The difference between 10W-40 and 5W-40 mainly lies in the number before the 'W'. 5W means it flows faster during cold starts in winter, lubricating the engine more quickly and making starts easier; 10W is slightly thicker and might be a bit slower in cold weather. However, the high-temperature number is the same at 40, so the protective performance is pretty much identical. Specifically, I used 10W-40 in the north, and the engine always felt a bit stiff during winter starts. After switching to 5W-40, it became much smoother. Choosing oil also depends on where you live: 5W-40 is more suitable for cold regions, while 10W-40 is sufficient in warmer areas. Don’t just focus on saving money—regular oil changes are essential to keep the engine healthy and reduce wear. In short, it’s a matter of adaptability; choosing the right oil for your climate brings peace of mind.

[RafaelAnn]

I've seen many car owners at the factory casually choose engine oil, only to end up with engine issues. The core difference between 10w-40 and 5w-40 lies in low-temperature fluidity: 5w flows as fast as water during cold starts, quickly lubricating the engine and reducing wear; 10w is slightly thicker, potentially causing slower starts in winter and increasing engine burden. However, both maintain a 40 rating at high temperatures, offering the same protection. For example, when customers complain about hard starts in winter, it's often found they're using 10w-40 - switching to 5w-40 solves the problem. My advice: don't just look at the oil can label, match it with your vehicle manual and local weather. Wrong choices can lead to premature wear, and extending oil change intervals might save money in the long run. Always prioritize 5w-40 unless you live in a warm climate.

[DelRose]

When I first bought a car, I was completely clueless. After researching, I understood the differences in engine oil. Simply put, the smaller number before the 'W' in 10W-40 and 5W-40 means better flow at low temperatures: 5W lubricates faster in cold weather, allowing the engine to start quicker; 10W is slightly slower but still usable. The high-temperature number (40) is the same, so performance in hot weather is identical. Choose based on climate: if you live in a cold area, 5W-40 is more reliable; in moderate regions, 10W-40 works fine too. I initially used the wrong oil, which caused startup noise, but later followed the manual and made the right choice. Don’t overthink it—beginners should ask mechanics or check the manual for safety.