The oil-free screw compressor element
No oil means that there is absolutely no oil for sealing the rotors 
and for cooling the compressed air, components and rotors. … The component is certainly cooled by cooling drinking water that flows through particular pockets in the element casing.
In a lubricated screw compressor, the lubricant will come in direct in contact with the compressor inlet air and compressed air. … The essential oil contains anti-oxidants to try to reduce the break down of the lubrication Oil-free Screw Air Compressor properties due to internal conditions.