What is the shelf life of fully synthetic engine oil?

[JuneLynn]

The shelf life of fully synthetic engine oil is approximately 5 years. The functions of engine oil are: 1. To alleviate friction and high temperature; 2. To reduce gas leakage and prevent external pollutants; 3. To prevent contact between water, air, acidic harmful gases, and components; 4. To buffer the pressure rise at the engine cylinder port; 5. To flush away dirt generated on the working surfaces of components. The steps for changing engine oil are: 1. Lift the vehicle, remove the underbody shield, and place a container of about 10 liters under the oil drain plug; 2. Unscrew the oil drain plug, use an air gun to blow into the oil filler port for two minutes, then tighten the oil drain plug after draining and wipe it with a tissue to check for leaks; 3. Reinstall the underbody shield and lower the vehicle, then use a funnel to add engine oil through the filler port.