The oil-free screw compressor element
No oil implies that there is absolutely no oil for sealing the rotors and for cooling the compressed air flow, elements and rotors. … The component is cooled by cooling water that flows through particular pockets in the 
element casing.
In a lubricated screw compressor, the lubricant comes in direct in touch with the compressor inlet air and compressed air. … The essential oil contains anti-oxidants to attempt to reduce the break down of the lubrication properties because of Oil-free Screw Air Compressor internal conditions.