10W40 engine oil is a more suitable choice in hot weather. Its high-temperature viscosity grade "40" can cope with high-temperature environments, ensuring that engine components form a stable oil film at high temperatures and reducing wear. This multi-grade lubricant combines low-temperature fluidity ("10W" indicates it maintains good fluidity at minus 25°C) with high-temperature protection, making it particularly suitable for older vehicles or those with significant engine wear, as the higher viscosity can compensate for increased component clearances. For new cars or precision engines, if the manual recommends low-viscosity oil (such as 5W30), 10W40 should be selected cautiously to avoid insufficient cold-start lubrication or reduced fuel efficiency due to excessive viscosity. In hot regions with prolonged high temperatures or frequent high-load operation, 10W40 provides more reliable high-temperature protection, but regular oil condition monitoring is necessary to ensure consistent performance.
