Newtonian fluids are those which flow newton law of viscosity and Non-Newtonian fluid are those that does not follow that rules. The Newtonian fluid viscosity is independent of the shear force applied on the system and its does not change with the change in the shear force for a given temperature. On the other hand the Non Newtonian fluids are those whose viscosity changes with change in shear force. They have four different conditions in this case; Dilatant, Pseudoplastic, Rheopectic, and Thixotropic
In the case of Newtonian fluid temperature effect the lubrication of steam turbine as increase in temperature decreases the viscosity of the lubricant and thus compromising the lubrication process. For Non Newtonian fluids the temperature and pressure both affects the lubrication process with high pressure increases the viscosity of the fluid.