In centrifugal compressors, there is no oil injection into a compression cavity. Oil is only used for bearing lubrication. In gear-drive designs, however, oil is used for lubrication of the gears. In centrifugal compressors, it appears that the direct-drive design is more suitable for refrigerant lubrication, as there is no requirement to lubricate the gears.

The ability to eliminate the need for oil lubrication would simplify designs and offer cost savings. Specific advantages of eliminating oil lubrication include removing many chiller failure modes associated with oil-based chiller lubrication systems, reducing the number of components, problems associated with oil and refrigerant mixing together and potentially more efficient operation.

Contamination of refrigerant by oil is also a factor in the heat transfer taking place in the heat exchangers used in the chiller. Oil tends to reduce heat-transfer efficiency. This means that an oil-free compressor could mean that higher chiller efficiencies are obtained, or, for a given efficiency, the heat exchanger could be of smaller size.
There is also an environmental benefit in not using oil, since the oil charge in a chiller can be lost during chiller repair, and oil would in one way or another end up contaminating the environment.