The aim of this study is to generate operational data that can be used to improve the production capacity in the Fluid Catalytic Cracking Unit (FCCU) in a Refinery and Petrochemical Company. This will aid in tackling the daunting challenge of unavailability of operational data that can be used to better understand and improve production capacity and ensure maximizing catalyst utilization. In addition, it addresses the challenges of analysis and control of the FCCU process due to its very complicated and little-known hydrodynamics, complex kinetics of both reactions of cracking and coke burning, strong interaction between the reactor and regenerator, and numerous operating constraints. Aspen HYSYS version 8.0 was used in modeling the cracking process using parameters extracted from the operating manual of the FCCU in the refinery. The operational data was used to compare the simulated effect of stepwise input in feed and reactor plenum temperatures as well as stepwise increase in reactor length on yield, catalyst-to-oil-ratio and catalyst regeneration. An optimum flow in naphtha was obtained by the interaction of the inlet crude flow rate, riser height, and temperature this optimum was supported by the study of the interaction of these parameters when, catalyst to oil ratio was set as the dependent parameter. The inferences drawn from the results are that the reactor plenum temperature of 560˚C and a riser length of 27 m are recommended for optimum performance that ensures lasting effect of an efficient catalyst activity.