Foam depressants control the tendency for foaming. Detergent and dispersant additives can facilitate aeration of oil, which results in foaming. This can reduce the lubricating ability of the oil, and interfere with the pumping of the oil. It is commonly added to hydraulic fluid to expedite foam breakup and releases dissolved air. It often does a good job in increasing the capacity of a given separator. However in sizing a separator to handle particular crude, the use of an effective depressant should not be assumed because characteristics of the crude and of the foam may change during the life of the field. Foam depressant allows more throughput than the design capacity.