What is the difference between 5W and 10W motor oil?
2 Answers
The main functions of motor oil are to reduce friction and wear between moving parts, and to remove sludge (one of the functions of dispersants) and varnish (cleaners) from the engine. The differences between 5W and 10W motor oil are as follows: 1. Different low-temperature performance: 5W has better low-temperature performance than 10W. If you are in a colder northern region, choose 5W or 0W. In southern regions, either 10W or 5W is suitable. 2. Different prices: 10W grade motor oil is generally cheaper than 5W. 3. Different low-temperature fluidity: The 'W' stands for winter, and the smaller the number before it, the better the low-temperature fluidity (oil thinning) of the motor oil. Therefore, 5W has better low-temperature fluidity than 10W. 4. Different protection capabilities for the engine during cold starts: 5W indicates that the motor oil can operate at a minimum temperature of -30 degrees Celsius, while 10W indicates a minimum operating temperature of -25 degrees Celsius.
I drove for many years in the north, and it was only during extremely cold winters that I truly understood the significance of motor oil viscosity grades. The difference between 5W and 10W mainly lies in low-temperature fluidity. The 'W' stands for Winter, and the lower the number, the better it performs in cold environments. With 5W, the engine starts very smoothly in sub-zero weather because the oil flows quickly to engine components, reducing wear. However, 10W is slightly thicker at low temperatures, making startup a bit slower, though it’s sufficient in the south or areas without extreme cold. When I used 10W in temperatures below -10°C, the engine felt sluggish, but switching to 5W solved the issue. This directly impacts winter driving safety—frequent startups can accelerate wear, so it’s crucial to consider local climate and seasonal changes when choosing oil. There’s also a second number, like 30 or 40, indicating high-temperature viscosity, but overall, selecting the right oil for freeze protection is key.
