Automotive engine oils are mainly divided into three categories by composition: mineral oil, semi-synthetic oil, and fully synthetic oil. Mineral oil is a base oil refined from crude oil. It is low-priced but has limited performance, making it suitable for low-emission economy vehicles. Its replacement interval is about 5,000 kilometres, though it exhibits weaker low-temperature performance. It is suitable for mid-range models with naturally aspirated engines, with a recommended replacement interval of 7,500 kilometres. It is particularly suitable for turbocharged or high-performance engines. Although more expensive, it provides extended oil change intervals (approximately 10,000 kilometres) and enhanced engine protection. Additionally, viscosity classifications include high-temperature grades (e.g., SAE 50), low-temperature grades (e.g., 5W), and multi-grade oils (e.g., 5W-30). The lower the number preceding "W", the better the low-temperature fluidity; the higher the number following "W", the greater the high-temperature viscosity. Selecting engine oil should consider the vehicle's engine type, operating conditions, and manufacturer recommendations. For instance, turbocharged models are advised to use fully synthetic oil, while conventional commuter vehicles may opt for semi-synthetic oil to achieve both cost-efficiency and adequate protection.
