What does the viscosity of oil mean and how does it affect the performance of machinery?

The viscosity of oil refers to its thickness or resistance to flow. It affects machinery performance by influencing how well the oil can lubricate moving parts. Higher viscosity oils are better at maintaining a lubricating film between parts, reducing friction and wear. However, if the oil is too viscous, it can impede the flow and cause issues with circulation and cooling in the machinery.