Abstract: The temperature of light straight run gasoline from a depropanizer tower is controlled as the function of the Reid Vapor Pressure change of a crude oil feeding a flash tower which provides an overhead product to the depropanizer tower and flashed crude oil to an atmospheric tower. The Reid Vapor Pressure is determined from the overhead product, the flashed crude, the pressure of the vapor in the flash tower and the temperature of liquid in the flash tower. A control unit includes a network which determines a change in the Reid Vapor Pressure as the quality of the feed crude oil to the flash tower changes. The network determines the change in the Reid Vapor Pressure and when the change exceeds a limit, provides a feed forward signal corresponding to a desired temperature associated with the new Reid Vapor Pressure. The desired temperature signal is determined in accordance with the equations hereinafter disclosed.