Kinematic Viscosity Test (ASTM D445) Procedure
KINEMATIC VISCOSITY TEST (ASTM D445) Kinematic viscosity is commonly determined under high temperatures using the American Society for Testing and Materials (ASTM D445) Viscosity Test. This test uses a uniformly marked or calibrated tube called a viscometer and a heating bath. The temperature of the bath is set at either 104 ° F (40 ° C), which is typical for industrial lubricants like hydraulic fluids, compressor oils or gear lubricants, or 212 ° F (100 ° C), which is typical for motor oils. The test oil is placed in a viscometer and heated by the bath to the specified stable temperature.
When the specified temperature is reached, the oil is drawn into a wider area within the viscometer, which is identified by upper and lower marks and allowed to drain out. The elapsed time can be directly converted into centistokes (cSt). To be relevant, the cSt number must be reported along with the temperature at which it was determined. It is important to note that when comparing fluid viscosities, fluids being compared must be tested at the same time and at constant temperatures, or the comparison is invalid. Although centistokes are the most common unit of measurement when determining kinematic viscosity, results may also be reported in units known as Saybolt Universal Seconds (SUS or SSU). Even though identical test temperatures may have been used to determine the oil’s viscosity in both centistokes and Saybolt Universal Seconds, the two should never be compared at face value because they are different units of measure. To do so would be similar to comparing distances in miles and kilometers. Viscosity reported in SUS is becoming increasingly rare.
OilBuddy’s Take
In other words, the KINEMATIC VISCOSITY test measures the flow of oil at different temperatures.