What does viscosity mean?

Viscosity is a measurement of the thickness and ‘ease of flow’ in any liquid. For example, water is a thin liquid that flows freely, so we say that it has a low viscosity. Honey, on the other hand, is relatively thick and flows more slowly. So we describe honey as having a high viscosity. It’s also worth noting that honey flows more easily – and is therefore less viscous – when it is slightly warm. Engine oil behaves in pretty much the same way, which is why mechanics will usually run an engine for a minute or two before draining used engine oil away to replace it.