You can also view previously answered questions in the HSW Question Archive . See this page for a description of the different ratings. A thin oil has a lower number and flows more easily, while thick oils have a higher number and are more resistant to flow. Water has a very low viscosity - it is thin and flows easily.
Honey has a very high viscosity - it is thick and gooey.
The higher the value, the more viscous the fluid. Since, viscosity varies inversely with temperature, its value is meaningless unless accompanied by the temperature at which it is determined. The centistoke rating is converted into the SAE weight designation using a chart like the one shown on this page . The polymers allow the oil to have different weights at different temperatures. The first number indicates the viscocity of the oil at a cold temperature, while the second number indicates the viscosity at operating temperature.