Which brand of fully synthetic engine oil is good?

[MacAdelyn]

Fully synthetic engine oils from Mobil and Castrol are good brands. Among domestic engine oils, brands like Jiahua, Kunlun, and Great Wall synthetic oils are also quite well-known. The functions of engine oil are: 1. To reduce friction and high temperatures; 2. To minimize gas leakage and prevent external pollutants; 3. To prevent contact between water, air, acidic harmful gases, and engine parts; 4. To cushion the pressure rise in the engine cylinder port; 5. To clean dirt generated on the working surfaces of parts. The method to check engine oil is: 1. Park the vehicle on a level surface; 2. Pull out the dipstick after the vehicle has been parked for 10 minutes; 3. Hold the dipstick perpendicular to the ground to check the oil level.