Using 5W-30 engine oil instead of 5W-20 usually does not cause direct damage to the engine, but careful selection is required based on the actual condition of the vehicle. The two have the same low-temperature performance (5W indicates adaptability to environments as low as -30°C), but differ in high-temperature viscosity: the kinematic viscosity of 5W-30 at 100°C is 9.3-12.5 mm²/s, slightly higher than that of 5W-20. Conversely, 5W-20 offers better fluidity, which can reduce fuel consumption in new cars (by approximately 3-5%) and optimize cold-start performance. If the vehicle manual explicitly specifies 5W-20, long-term substitution with 5W-30 may result in a slight increase in fuel consumption (around 0.3-0.5 L per 100 kilometres) or marginally weaker low-speed power response. However, for older vehicles with over 100,000 kilometres and increased piston clearance, 5W-30 can help reduce oil consumption. If adjusting viscosity is necessary, factors such as vehicle age, climate (tropical regions may favor 5W-30), and driving habits (aggressive driving requires higher viscosity) should be comprehensively evaluated, while monitoring changes in oil consumption.
