Newtonian fluids (including lubricating oils) behave in the following way: Consider any fluid between two parallel plates of area A and separated by a distance H. One plate is held fixed whilst the other moves with velocity V. As it moves it carries the layer of fluid touching it, which in turn carries along the layer of fluid closest to it and so on. The layer of fluid adjacent to the stationary plate will also be stationary so that the velocity of the different layers of fluid will vary between 0 and V if there is laminar flow. The force required to cause this flow is given by the following equation:
F=ηAV/H
The constant of proportionality (η) is the viscosity of the fluid and represents the resistance to flow at a particular temperature. It is dependant on the nature of the fluid and the temperature only.