Hydraulic fluid is the magic juice that allows our machines to push, pull, raise, and lower incredible weights.
Without diving deep into the mechanics of hydraulics, a small force is applied to one end of a column of hydraulic fluid which affects a much greater force on the other end, thanks to mechanical advantage of force over different sized areas. This works due to the fact that fluids do not compress very much, so you can exert tremendous pressure through them without losing hardly any force.
So what are these super fluids? The common three are mineral oil, organophosphate ester and polyphaolefin. Many others exist though. There is a complex mixture of additives in the oil that determine its properties. For example, some applications may require very high operating temperatures while other necessitate relatively low viscosity. The functions of brake fluid call for a mixture that can endure high heat during operation and refrain from freezing during the winter months.
Hydraulic fluids can be found everywhere. Brake systems, power steering systems, forklifts, fence post drivers, aircraft control systems, presses, lifts, excavators, pallet jacks, shock absorbers, spreaders, impact wrenches, crimpers and even diamond chainsaws operate on hydraulic pressure. You can go to your local auto parts shop and buy a hand operated hydraulic jack that will lift 60,000 pounds!
The next time you need something moved, think about squeezing liquids! | 
