A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water.[1] Examples of equipment that might use hydraulic fluids are excavators and backhoes, hydraulic brake,power steering systems, transmissions, garbage trucks,aircraft flight control systems, lifts, and industrial machinery.
| Function | Property |
| Medium for power transfer and control |
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| Medium for heat transfer |
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| Sealing Medium |
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| Lubricant |
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| Pump efficiency |
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Special function |
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Environmental impact |
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Functioning life |
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