What is the difference between 5w20 and 5w30?

[LaMichael]

5w30 engine oil has a higher viscosity than 5w20 engine oil, but the low-temperature flow performance of these two oils is the same. The viscosity of engine oil changes with temperature, so special attention should be paid to its performance under both low and high-temperature conditions. For example, in 5W-30, the first number indicates low-temperature fluidity. 5W means it can withstand low temperatures of -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 second number represents the kinematic viscosity of the oil at 100°C. The higher this number, the better the oil maintains its viscosity at high temperatures, which can also be understood as better lubrication performance under high-temperature conditions. Relatively speaking, better low-temperature fluidity makes cold starts smoother and provides better engine protection. The viscosity of engine oil 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 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 slightly shorter, requiring a change every 7,000 kilometers or six months. When selecting engine oil, consider the following: Choose oil based on the engine's requirements. There is no need to use high-grade oil in engines with lower requirements, nor should lower-grade oil be used in engines with higher requirements. Multi-grade oil is recommended because it is economical, long-lasting, and efficient, providing better engine protection. Due to its characteristics, multi-grade oil may darken prematurely and have lower oil pressure compared to conventional oil, which is normal. Since engine oil significantly impacts engine performance and lifespan, always follow the vehicle's manual for selecting the same series, performance grade, and viscosity grade. The oil recommended in the vehicle manual is based on the engine's performance and the regional climate, providing guidance with a significant safety margin.

[LeJohn]

I've been driving for years and enjoy researching motor oil. The main difference between 5W20 and 5W30 lies in their high-temperature viscosity. The 5W part indicates identical cold-start performance, suitable for winter starts. But the 20 or 30 number represents the oil's thickness when the engine is hot: 5W20 is thinner, which can slightly improve fuel efficiency and potentially save some gas money, making it ideal for modern fuel-efficient engine designs - like my Toyota compact car which specifies 5W20; 5W30 is slightly thicker, offering better protection for engine components at high temperatures, especially suitable for older vehicles or high-load driving. When I used the wrong type, I noticed increased engine noise and slightly higher fuel consumption, so it's best to check the owner's manual for the correct oil - otherwise it may affect engine lifespan and performance. In short, don't switch oils arbitrarily, matching your vehicle model is what matters most.

[LaAmelia]

As a car enthusiast, I often help friends check their engine oil. The prefix 5W in both 5W20 and 5W30 indicates similar low-temperature fluidity, making cold starts easier. The difference between the suffixes 20 and 30 lies in the high-temperature viscosity grade: 20 has lower viscosity, flows faster, and can reduce friction under normal driving conditions to improve fuel economy; 30 has higher viscosity, providing stronger protection against overheating and wear. I've seen test reports showing that 5W20 is suitable for the precise design of new car engines, while 5W30 is better for older cars or frequent high-speed driving scenarios. Mixing them can lead to unstable oil pressure or accelerated wear, so it's recommended to choose oil according to the manufacturer's recommendations and also consider environmental temperature changes.