Oil Lubricated Piston Compressor:
An Oil-lubricated Piston compressor is one that has its pistons, cylinders and cranks lubricated by oil circulating in the compressor. The compressed air from an oil-lubricated reciprocal compressor contains a certain amount of residual oil, typically 10-15 mg/m¢.
Oil-free Piston Compressor:
An Oil-free piston compressor is one which is not lubricated by oil and as a result the compressed air produced is free of residual oil. Most versions of oil-free reciprocal compressors have permanently lubricated bearings. The pistons in these compressors have grease-free piston rings, usually made of Teflon or carbon fibre. This type of compressor typically requires more frequent replacement of bearings and piston rings than the oil-lubricated versions.