1. Functions and demands of hydraulic fluids

Generally speaking, there are 21 characteristics or qualities to consider [1] . It is interesting to enumerate them:

• stability to heat, oxidation and hydrolysis ;

• viscosity-temperature properties ;

• fire resistance ;

• compressibility modulus ;

• lubricity ;

• compatibility and non-corrosivity with respect to the materials making up the hydraulic system ;

• volatility ;

• radiation resistance ;

• deterioration trend ;

• cost factor given performance ;

• length...