For high-mileage vehicles (typically those with over 100,000 kilometres driven), whether 5W-30 engine oil is suitable requires comprehensive evaluation of the engine's wear condition and usage scenarios. However, high-mileage engines with increased component clearances may require higher-viscosity 5W-40 oil to enhance oil film thickness (providing approximately 20% higher high-temperature viscosity), thereby reducing oil consumption and improving sealing performance. If the owner's manual permits and the engine exhibits no significant oil burning (e.g., consuming less than 0.5L per 5,000 kilometres), full synthetic 5W-30 may continue to be used, though shortening the change interval to 8,000 kilometres is recommended. Should abnormal consumption occur or the vehicle operate frequently under high-temperature, high-load conditions (such as extended highway driving or heavy towing), upgrading to 5W-40 is advisable. German turbocharged vehicles or high-mileage cars in southern high-temperature regions are better suited for 5W-40, while well-maintained Japanese/Korean naturally aspirated models may retain 5W-30 for optimal fuel efficiency (saving 0.3-0.5L per 100km). Regular inspection of dipstick oil level and condition is essential, with all viscosity adjustments being performance-driven.
