Abstract: A method for controlling an additive blending process includes determining the volume of main product and blending an amount of additive thereto to obtain a predefined ratio of additive to main product. The method includes the step of creating a non-volatile record of each significant event which occurs during blending operations and includes an extensive error checking and safety regime. A controller for accomplishing this method includes the ability to blend multiple additives simultaneously and with different types of blending systems such as piston injectors and streaming. The controller monitors status signals from the system and removes enabling signals from various components to effect a safe shut down in the event of an error condition being detected.