viscosity is the fluid resistance against flow
oil viscosity units is centipoise or centistoke (cp)

The viscosity of diesel fuel is directly dependent upon the temperature at which it's kept. At 100 degrees, the viscosity may be as much as 140 SSU. The higher the temperature, the lower SSU, so at 130 degrees the viscosity may only be 70 SSU.

yes viscosity is a property of gas

If something has a greater viscosity, it becomes more 'runny' compared to its original state when heated up. The greater the change from thick to runny = the greater the viscosity. So honey has a greater viscosity than water for example.

Viscosity is the measure of a fluids resistance to flow. The higher the viscosity the more viscous (the more resistance it has to flow); honey is generally much more viscous than water.