What is the difference between oil and oil-free air compressors

The oil and non-oil in the air compressor generally refer to the oil content of the exhaust gas of the air compressor. Generally, the oil content of the oil machine is larger, and the oil content of the oil-free machine is 0.01ppm, so use this The oil content is used to distinguish the air compressor with oil and without oil. There is also a completely oil-free air compressor, which is not lubricated with oil, but with resin lubrication, so the final gas discharged without oil is called a completely oil-free air compressor