How to Add Refrigerant Oil to an Automobile Compressor?

[StevenDella]

If adding directly from the compressor, first perform an oil return operation, with the control system operating at the coldest setting and highest fan speed for 20 to 30 minutes. When adding from the high-pressure side, evacuate to 98kPa, then close the high-pressure side manual valve and the service valve on the compressor. When adding from the low-pressure side, no service valve is needed. After evacuating to 98kPa, close the low-pressure side manual valve and continue evacuating with the vacuum pump.