The choice between 5W30 and 10W40 engine oils should be comprehensively determined based on vehicle condition, climatic conditions, and driving habits. 5W30 has a kinematic viscosity of 9.3-12.5 mm²/s at 100°C, with a relatively thin oil film and excellent fluidity. It is suitable for new cars or low-wear engines (such as Japanese and Korean models). It exhibits superior low-temperature starting performance and can reduce fuel consumption by approximately 3%-5%, making it ideal for urban commuting and environments with temperatures ≤ 30°C. 10W40 has a higher high-temperature viscosity (12.5-16.3 mm²/s), a thicker oil film, and strong sealing properties. It can fill component gaps in older engines (with mileage ≥ 80,000 km) or German turbocharged vehicles, providing more stable lubrication protection under high-temperature, heavy-load, or aggressive driving conditions. However, fuel consumption will slightly increase by 0.3-0.5 L/100 km. For climate, 5W30 is recommended for cold northern regions to optimize cold starts, while 10W40 is preferred for high-temperature southern areas or long-distance highway driving to enhance high-temperature stability. Blindly choosing high-viscosity oil may lead to increased fuel consumption or oil passage blockage. For example, 5W30 is suitable for precision engines, while 10W40 is chosen for high-wear models.
