It was not included in this article for that reason. Other multigrade synthetics may not use VI improvers either. The full literature available from the oil company should include this information. Follow your manufacturer's recommendations as to which weights are appropriate for your vehicle. Viscosity Index is an empirical number indicating the rate of change in viscosity of an oil within a given temperature range.
Higher numbers indicate a low change, lower numbers indicate a relatively large change.
The higher the number the better. This is one major property of an oil that keeps your bearings happy. These numbers can only be compared within a viscosity range. It is not an indication of how well the oil resists thermal breakdown. Flash point is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil.