The compressor oil filters task is to remove all wear-promoting impurities from the refrigerant oil without separating any special additives. Therefore, oil filters purpose is to protect compressors. And also to protect oil level regulators from damage.
In both oil free and oil injected compressors the compressor oil is used for lubrication of the compressor element bearings. And also it drives shaft bearings as well as the gears. Additionally, any dust or dirt ingression will damage the rollers of these bearings and the gear contact surfaces. Therefore, wear of the bearings or damage to the gears will eventually result in rotor contact. As a result the performance loss and reduced compressor element life will occur.
Further damage to the bearing rollers will result in cage-breakage and ultimately complete destruction of the compressor element.