ASTM D6080 REV A: Standard Practice for Defining the Viscosity Characteristics of Hydraulic Fluids

This practice covers all hydraulic fluids based either on petroleum, synthetic, or naturally-occurring base stocks. It is not intended for water-containing hydraulic fluids. 

For determination of viscosities at low temperature, this practice uses millipascal·second (mPa·s) as the unit of viscosity. For reference, 1 mPa·s is equivalent to 1 centipoise (cP). For determination of viscosities at high temperature, this practice uses millimetre squared per second (mm²/s) as the unit of kinematic viscosity. For reference, 1 mm²/s is equivalent to 1 centistoke (cSt). 

This practice is applicable to fluids ranging in kinematic viscosity from about 4 to 150 mm²/s as measured at a reference temperature of 40°C and to temperatures from -50 to +16°C for a fluid viscosity of 750 mPa·s.

NOTE 1—Fluids of lesser or greater viscosity than the range described in 1.3 are seldom used as hydraulic fluids. Any mathematical extrapolation of the system to either higher or lower viscosity grades may not be appropriate. Any need to expand the system should be evaluated on its own merit.

The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

*A Summary of Changes section appears at the end of this standard

Brookfield viscosity

hydraulic fluid

shear stability

viscosity

viscosity classification