Question 1

How do you convert kinematic viscosity (cSt) to dynamic viscosity (cP)?

Accepted Answer

Multiply the kinematic viscosity by the fluid's density (specific gravity) at the target temperature. For example, a PAG oil with a viscosity of 100 cSt and density of 1.05 g/cm³ has a dynamic viscosity of 105 cP.

Question 2

What is the difference between ISO VG and SAE viscosity grades?

Accepted Answer

ISO VG is the global standard for industrial lubricants, measuring kinematic viscosity in cSt at 40°C. SAE grades define viscosity ranges for automotive engine and gear oils, measured at both low temperatures and 100°C, and do not align directly with ISO VG numbers.

Question 3

Why is density critical when performing lubricant unit conversions?

Accepted Answer

Density is critical because synthetic fluids like PAGs have a specific gravity greater than 1.0, meaning they are denser than water. Mineral oils are lighter (0.85-0.90), and this density difference significantly impacts the relationship between kinematic and dynamic viscosity.

Question 4

How do I convert Saybolt Universal Seconds (SUS) to centistokes (cSt)?

Accepted Answer

At 100°F, for values above 70 SUS, you can approximate cSt by dividing the SUS value by 4.635, or use our automated converter to run the standard ASTM D2161 conversion equations.

Viscosity and Lubricant Unit Converter