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Viscosity Information

Viscosity
Measurement of a fluid's resistance to flow. The common metric unit of absolute viscosity is the poise, which is defined as the force in dynes required to move a surface one square centimeter in area past a parallel surface at a speed of one centimeter per second, with the surfaces separated by a fluid film one centimeter thick. In addition to kinematic viscosity, there are other methods for determining viscosity, including Saybolt Universal Viscosity (SUV), Saybolt Furol Viscosity, Engier Viscosity, and Redwood Viscosity.  Since viscosity varies inversely with temperature, its value is meaningless until the temperature at which it is determined is reported.

Viscosity Index
A commonly used measure of a fluid's change of viscosity with temperature. The higher the viscosity index, the smaller the relative change in viscosity with temperature.

Viscosity Grade
Any number of systems which characterize lubricants according to viscosity for particular applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft piston engine oils.

 

ISO Viscosity Grade Conversions
ISO
Viscosity
Grade
Mid-point
Kinematic
Viscosity
Kinematic Viscosity Limits cSt at 40° (104°F) ASTM, Saybolt
Viscosity Number
Saybolt Viscosity SUS
Min. Max. Min. Max.
2 2.2 1.98 2.42 32 34.0 35.5
3 3.2 2.88 3.52 36 36.5 38.2
5 4.6 4.14 5.06 40 39.9 42.7
7 6.8 6.12 7.48 50 45.7 50.3
10 10 9.00 11.0 60 55.5 62.8
15 15 13.5 16.5 75 72 83
22 22 19.8 24.2 105 96 115
32 32 28.8 35.2 150 135 164
46 46 41.4 50.6 215 191 234
68 68 61.2 74.8 315 280 345
100 100 90.0 110 465 410 500
150 150 135 165 700 615 750
220 220 198 242 1000 900 1110
320 320 288 352 1500 1310 1600
460 460 414 506 2150 1880 2300
680 680 612 748 3150 2800 3400
1000 1000 900 1100 4650 4100 5000
1500 1500 1350 1650 7000 6100 7500