Pressure viscosity sensitivity


 Dynamic viscosity at atmospheric pressure η0 10-3 PaĚs
 Pressure viscosity coefficient α 10-9 1/Pa
 Pressure of interest p 106 Pa
   
 Viscosity ratio Barus η/η0 -
 Viscosity ratio Roelands η/η0 -
The Barus equation is accurate only for pressures up to 0.1 GPa. For higher pressure the Roelands equation gives the best result.
 
Lubricants Dynamic visc η0
[mPaĚs]
Pressure-visc
coeff α [10-9 m2/N]
30 60 100 30 60 100
High VI oils            
Light machine oil 38 12.1 5.3 - 18.4 13.4
Heavy machine oil 153 34 9.1 23.7 20.5 15.8
Heavy machine oil 250 50.5 12.6 25.0 21.3 17.6
Cylinder oil 810 135 26.8 34.0 28.0 22.0
Medium VI oils            
Spindle oil 18.6 6.3 2.4 20 16 13
Light machine oil 45 12 3.9 28 20 16
Medicinal white oil 107 23.3 6.4 29.6 22.8 17.8
Heavy machine oil 122 26.3 7.3 27.0 21.6 17.5
Heavy machine oil 171 31 7.5 28 23 18
Low VI oils            
Spindle oil 30.7 8.6 3.1 25.7 20.3 15.4
Heavy machine oil 165 30.0 6.8 33.0 23.8 16.0
Heavy machine oil 310 44.2 9.4 34.6 26.3 19.5
Cylinder oil 2000 180 24.0 41.5 29.4 25.0
Other fluids / lub's            
Water 0.90 0.47 0.28 0 0 0
Castor oil 360 80 18.0 15.9 14.4 12.3
Glycerol 535 73 13.9 5.9 5.5 3.6
PP glycol 750 82.3     17.8    
PP glycol 1500 177     17.4    
Tri-arylphosphate ester 25.5     31.6    
Table adapted from page 21 Engineering Tribology Second Edition
www.tribology-abc.com