What are the functions of engine oil?

[McJordan]

The functions of engine oil are: 1. To separate the surfaces of relatively sliding parts, thereby reducing wear; 2. To bring heat back to the oil tank and then dissipate it into the air to help the radiator cool the engine; 3. To circulate carbon deposits, sludge, and metal wear particles from engine parts back to the oil tank, flushing away dirt generated on the working surfaces of the parts through the flow of the lubricating oil. The classifications of engine oil are: 1. Conventional mineral oil; 2. Semi-synthetic oil; 3. Fully synthetic oil. The signs that engine oil needs to be changed are: 1. Check the viscosity of the oil—if there is no viscosity, the oil needs to be changed; 2. The color of the oil is black; 3. There are too many black particles, metal shavings, or carbon deposits in the oil; 4. The smell of the oil is abnormal.