The oil-free screw compressor element
No oil means that there is no oil for sealing the Oil-free Screw Air Compressor rotors and for cooling the compressed surroundings, components and rotors. … The element is definitely cooled by cooling drinking water that flows through unique pockets in the component casing.
In a lubricated screw compressor, the lubricant comes in direct in touch with 
the compressor inlet air and compressed air. … The oil contains anti-oxidants to attempt to reduce the breakdown of the lubrication properties due to internal conditions.