What is the difference between 10W50 and 10W40 engine oil?
2 Answers
10W30 and 10W40 engine oils have the following differences: 1. Although 10W30 and 10W40 have the same low-temperature fluidity, their high-temperature viscosities differ. 2. 10W30 has lower high-temperature viscosity, better fluidity, and can reduce fuel consumption more effectively. It also allows the engine to dissipate heat faster. However, it may result in relatively louder engine noise during operation. 3. 10W40 has higher high-temperature viscosity and is thicker. It enables the engine to handle greater loads, produces less noise, has smaller fluctuations, and is more stable. However, its poorer fluidity creates more resistance for internal engine components and consumes more fuel. 4. Generally, 10W30 oil with lower viscosity and better fluidity provides better engine performance. 5. Although 10W30 is more fuel-efficient and offers better performance, its high-temperature shear resistance is weaker, making the oil film prone to rupture and causing greater wear compared to the higher-viscosity 10W40. On the other hand, 10W40, despite its poorer fluidity, higher resistance, and higher fuel consumption, delivers more stable performance, ensuring normal engine operation under high temperatures. 6. Typically, Japanese naturally aspirated engines are better suited for low-viscosity 10W30 oil, while German turbocharged engines perform better with high-viscosity 10W40 oil. Choosing engine oil should not only consider performance but also require a comprehensive evaluation to select the most suitable oil for your car's engine.
I've done quite a bit of research on oil viscosity. The 10W in 10W50 and 10W40 indicates that both have essentially the same cold-start flow performance at low temperatures like -20°C, making them suitable for winter use. But the key difference lies in the latter part: 50 and 40 represent high-temperature viscosity ratings. A 50-grade oil is thicker at high engine operating temperatures, providing extra protection—ideal for high-performance cars, racing vehicles, or hot climates to prevent oil thinning and wear. A 40-grade oil is thinner at 100°C, better suited for daily driving like commuting, offering lower fuel consumption and broader compatibility. Oil selection should consider vehicle age: older cars may benefit from 50-grade for enhanced sealing, while newer cars perform best with 40-grade for balanced performance. Having driven various vehicles, I've observed that even subtle viscosity differences significantly impact engine longevity. When the manual doesn't specify, adjusting for climate is a smart approach.
