The Fluidized catalytic cracking (FCC) unit is the heart of most modern high conversion refineries. It is a very flexible unit, and it can process a wide variety of feeds. Tighter crude supply affects the FCC. Feed quality to most FCC units is becoming heavier, and feed quality is no longer constant on most FCCs. As more crude is imported, the crude quality changes are depending on the source. FCC feed quality is rarely constant any more. In order to process difficult feeds and obtain better quality yield, modern refineries optimize FCC catalyst selectivity. This paper demonstrates the need for dynamic catalyst optimization, and shows how this process can easily be achieved by using catalytic additives. An example is given in this paper where this approach has been implemented. Effective catalyst management processes, and the automated addition systems required to implement this strategy, are also discussed.