Hydraulic Fluid
Used to transmit power, the heart of any hydraulic system is a hydraulic pump. Keeping the pump, as well as other components, working at peak performance during high loads, hydraulic fluids must be kept at the recommended levels and must be changed periodically. Avoid lack of lubrication or noisy pumps by using high-quality hydraulic fluid in your hydraulic system.
To learn more about the purpose, maintenance and more, here.