Which of the following is the temperature at which lubricant will start to flow when poured?

Explanation:

Pour point 

• The temperature at which the lubricant is able to flow when poured or
• It is the temperature below which the liquid loses its flow characteristics.

Dynamic viscosity (μ)

• It is the property of a fluid that offers resistance to the movement of one layer of fluid over the adjacent layer of the fluid.
• Shear stress between two layers of fluid is directly proportional to the rate of change of velocity with respect to perpendicular distance from a fixed point.
• Unit – kgm^-1s^-1

Kinematic Viscosity (ϒ):

• It is the ratio of dynamic viscosity to the density of fluid flowing
• \({\rm{Kinematic\;Viscosity\;}}\left( {\rm{\gamma }} \right) = {\rm{\;}}\frac{{{\rm{Dynamic\;viscosity\;}}\left( {\rm{\mu }} \right)}}{{{\rm{density\;}}\left( {\rm{\rho }} \right)}} \)
• Unit is – m²s^-1

Important Points

With the movement of the two mating parts of the machine, heat is generated. If it is not controlled the temperature may rise resulting in total damage to the mating parts. Therefore, a film of a cooling medium with high viscosity is applied between the mating parts which are known as a lubricant.

Properties of lubricant