Hydraulic fluids that are too cold or too hot can steal years of service life from expensive hydraulic components. In cold temperatures, where fluid viscosity can be extremely high*, a lack of lubrication can be especially damaging to the hydraulic pump. Similarly, in very hot temperatures, where viscosity values can be quite low**, hydraulic hoses are quite vulnerable to hardening and then eventually cracking or breaking.
* viscosity in the range of 1,000 to 5,000 mm/s2
** viscosity in the range of 1 to 5 mm/s2