What is the temperature and units of measure for the ISO VG system?

The ISO VG (International Organization for Standardization Viscosity Grade) system specifies the viscosity of lubricating oils based on their measured kinematic viscosity at a specific temperature of 40 degrees Celsius (40C). The unit of measurement used within this system is centistokes (cSt), which is a measure of kinematic viscosity.

Kinematic viscosity is a measure of a fluid's internal resistance to flow under the influence of gravity, and using centistokes as the unit allows for a standard reference to evaluate the performance of lubricants under specified temperature conditions. Therefore, the relationship provided by the ISO VG system specifically focuses on the oil's viscosity at 40C in centistokes, making this option the accurate representation of the standard criteria defined by ISO.

Other options incorrectly reference different temperatures, units, or practices that do not align with the ISO VG specification for lubricants.