5W30 and 5W40 engine oils have the same low-temperature performance (both suitable for -30℃ environments), but their high-temperature viscosities differ significantly. The high-temperature kinematic viscosity of 5W30 is 9.3-12.5 mm²/s, which has better fluidity. It is suitable for new cars or low-mileage vehicles (under 100,000 km), as it can improve cold-start performance and reduce fuel consumption by approximately 0.3-0.5 L per 100 km. It is particularly suitable for Japanese, Korean, and American models as well as urban commuting scenarios. The high-temperature kinematic viscosity of 5W40 is 12.5-16.3 mm²/s, forming a thicker oil film. It can compensate for wear gaps in older engines and reduce oil consumption (with actual consumption reduced by over 50%), making it more suitable for German turbocharged vehicles, high-mileage cars, or high-temperature long-distance driving. When selecting oil, always prioritize the vehicle manufacturer's recommendations: use 5W30 for new cars or mild driving conditions, while 5W40 is required for older vehicles or high-temperature, high-load operating conditions. Additionally, regularly check the oil dipstick to monitor consumption levels.
