What are the differences between 5W30 and 10W40?
2 Answers
The main difference between 5W30 and 10W40 is their viscosity. 10W40 oil has a higher viscosity, while 5W30 oil has a relatively lower viscosity. Additionally, 5W30 oil can adapt to lower temperatures compared to 10W40. 5W30 and 10W40 are SAE grades that indicate the viscosity of the oil. The "W" stands for winter, and the number before it represents the lowest environmental temperature at which the oil can be used. A lower number indicates better engine protection during cold starts. There are also differences in the types of vehicles that use these two oils: High-viscosity oils (with higher values) may be more suitable for high-speed driving or heavy-load vehicles. For older vehicles, using 10W-40 oil may result in slightly louder engine noise compared to 5W-30. The viscosity of engine oil changes with temperature, so it's important to pay attention to its performance under both low and high temperatures. For 5W-30, the first number indicates low-temperature fluidity. 5W means it can withstand temperatures as low as -30°C. The smaller this number, the better the low-temperature fluidity: 0W is -35°C; 5W is -30°C; 10W is -25°C; 15W is -20°C; 20W is -15°C; 25W is -10°C. Better low-temperature fluidity ensures smoother cold starts for the vehicle. The number after the "W" represents the kinematic viscosity of the oil at 100°C. A higher number means the oil can maintain its viscosity better at high temperatures, which can also be understood as better lubrication performance under high-temperature conditions. Generally, better low-temperature fluidity ensures smoother cold starts and better engine protection. Engine oil viscosity should not be too high or too low. If the viscosity is too low, it can increase engine wear. If the viscosity is too high, it can increase engine resistance during operation, leading to reduced engine power and increased fuel consumption. When the engine is running, the oil forms a film on the surfaces of engine components, reducing friction and lowering resistance. If the oil viscosity is too low, it cannot form a stable film, which can accelerate engine wear. For full synthetic oil, the recommended replacement interval is one year or 10,000 kilometers. For semi-synthetic oil, the replacement interval is shorter, typically every 7,000 kilometers or six months. When choosing engine oil, consider the following: Select oil based on the engine's requirements. There's no need to use overly advanced oil for engines with lower requirements, nor should you use lower-grade oil for engines with higher requirements. Multigrade oil is recommended because it is economical, long-lasting, and efficient, providing better protection for the engine. Due to its properties, multigrade oil may appear darker and have lower oil pressure than conventional oil during use, which is normal. Since oil significantly affects engine performance and lifespan, always follow the vehicle's manual to select oil of the same series, service grade, and viscosity grade. The oil recommended in the vehicle manual is based on the engine's performance and the climate of the sales region, providing guidance with a considerable safety margin.
In my over ten years of driving in Northeast China, I've found the main difference between 5W30 and 10W40 lies in their performance in cold environments. The '5W' in 5W30 indicates lower viscosity at low temperatures, providing better oil flow for quicker engine lubrication during sub-zero starts and smoother acceleration, making it ideal for northern winters. In contrast, the '10W' in 10W40 means higher viscosity in cold weather, resulting in slower oil flow during startup, which may increase engine wear. I've also noticed that 5W30 can slightly save fuel costs due to faster lubrication. However, for older vehicles or engines with larger clearances, the thicker protective layer of 10W40 can compensate for wear and extend engine life. Ultimately, choosing oil should follow the owner's manual and environmental conditions to avoid long-term issues like carbon buildup from using inappropriate oil.
