Reduce maintenance costs: The overall maintenance costs of hydraulic pumps are greatly reduced because they are self-lubricating and do not have problems associated with pumps that rely on compressed air, such as moisture, oil-based clearing, scaling, and rust. They also eliminate the problem of icing, which occurs when the circulation of the pump causes the cooling of the rapidly discharged compressed air.http://www.oilmaxhydraulic.com/hydraulic-pumps-parts/