With the advent of the next passenger car motor oil specifications, API SL, many motor oils will have to be blended to much lower volatility than they currently are. In order to do this, a special low volatility cut of base stock will have to be included in many oils, particularly 5W30's. It is of interest to know how the volatility of a finished lubricant varies as a function of the volatility of it's components in order to make these oils in an optimal way. In this paper it is shown how volatility, namely TGA NOACK and ASTM D2887E, can be modeled as a function of the volatility of the components used in the blend. This was accomplished using a statistically designed mixture experiment. The resulting model was then validated by running confirmation blends which fell in the original design region. Using the results of this design coupled with the confirmation blends, feasible regions are defined which meet the API SL requirements while accounting for inherent variability.