Kinematic Viscosity :
Kinematic viscosity characterizes the speed at which a fluid flows from Point A to Point B at a given temperature. The reference temperatures are 40°C and 100°C.
ISO viscosity is expressed in square millimetres per second (mm2/s), at 40°C or 100°C.
Viscosities have been ISO standardized (International Standard Organisation). The ISO grade enables tolerance of +/- 10% with respect to the reference value.
Viscosity Index (VI) :
Viscosity is affected by changes in temperature. Viscosity drops when the temperature increases. And inversely, viscosity increases when the temperature drops.
At a high temperature, viscosity must be sufficient enough to form a lubricant film. At a low temperature, viscosity must not be too high, as the lubricant must run and be pumpable.
The Viscosity Index defines the relationship between viscosity and temperature.
Flash Point (FP) :
This is the temperature at which the most volatile oil vapours ignite briefly when in contact with a flame. The temperature is not high enough for combustion to self-sustain.
Fire Point (ignition point) :
Temperature at which the most volatile oil vapours ignite when in contact with a flame and continue to burn. Combustion begins.