Hydraulic oil coolers, also called heat exchangers, use air or water to cool fluid in hydraulic systems. They pass oil through a coil or core to cool the oil before it enters the system. Heated oil causes excess wear on seals, surfaces, and other components, which can cause particulate buildup, damage components, and shorten the system's life span. Water oil coolers are compact and can be used in high-pressure applications such as those found in oil refineries and chemical processing plants. Air oil coolers pass heated fluid through a radiator-like core and use ambient air to cool hydraulic fluid. They do not require access to a power source, making them suitable for mobile applications where access to a power source is limited. Forced-air oil coolers have a fan that pushes air over the surface of the coil or core, and they require a power source. Off-line forced-air oil coolers have a separate motor and filter to cool and filter hydraulic fluid apart from the hydraulic system.