eli5: If water is non-compressible, then why not use it in hydraulic machines instead of hydraulic oil?

Question

eli5: If water is non-compressible, then why not use it in hydraulic machines instead of hydraulic oil?

In: 1817

Answer 1

Water changes density quite a bit with temperature which would affect the performance of the system. Water is also highly polarized and thus may cause corrosion and rust to form in the system. Using an oil helps both with keeping a more stable density profile over various temperatures and is less reactive than water.