Fluid Catalytic Cracking Unit (FCCU) is a process used by refineries to convert heavy oil fractions into lighter products such as gasoline and diesel fuel. It involves breaking down large molecules into smaller ones using a catalyst and high temperatures. The FCCU process is an important part of the refining process, as it increases the yield of valuable products. The FCCU has become the benchmark for many advanced control techniques in recent decades. Both the academic and the industrial researchers show interest in developing a new control algorithm for the efficient industrial FCCU implementation in-order to attain economic and efficient test bench. As a highly non-linear and interacting process, modeling and controlling FCCU is a difficult problem. In this study, the simulation response of gain scheduling decentralised mixed fuzzy logic controller (GSM-FLC) and gain scheduling decentralised fuzzy logic controller (GSD-FLC) are attained on the FCCU process. Real-coded genetic algorithms (RGAs) are used to optimize GSD-FLC and GSM-FLC parameters such as membership functions, rules, and scale factors. Finally, the simulated results are used to compare the response of the, GSD-FLC scheme and GSM-FLC scheme.