“This Article tells us how quickly or slowly the motor flows – and about the measure of its resistance to flow. Oil viscosity is the measure of its resistance to flow. Motor oil viscosity is the measure of its resistance to flow. Low-viscosity oil (e.g. 0W-20) flows faster than high-viscosity oil (e.g. 20W-50). It discusses oil viscosity and what does it mean? It explains how viscosity is the measure of internal friction or its resistance to flow. Thin and light is low viscosity and thick and heavy is high viscosity.
It also explains why viscosity is the most important part of a lubricant and how well it protects your vehicle. Different vehicles require different viscosity oil and the ability to resist thickening. Amsoil Synthetic Motor Oils resist thickening under extreme heat and will flow in sub-zero temperatures when conventional oils will not. Too low viscosity can cause the increased metal to metal contact and wear.”