Coker gas oil (CGO), heavy cycle oil (HCO), and a CGO-HCO blend were treated by solvent refinement and then cracked in a FCC pilot plant over a commercial Y zeolite-based catalyst at selected reaction conditions. The experimental setup simulates the cracking behavior of different feed streams in an FCC unit using different processing schemes. The processing alternative that can yield the highest conversion and maximum light oil production was evaluated. Blending unrefined CGO into FCC feedstock results in decreased feed conversion and retarded desirable product yields. This is attributed to the large amount of basic nitrogen compounds and polycyclic aromatics found in unrefined CGO. Solvent refinement of CGO, however, produced significant improvements in product yield, denitrification and contaminant-removal rates, and product quality. The same observations are true for feedstocks blended individually with refined HCO and a refined mixture of CGO and HCO. Refined oils are also superior to RFCC feedstocks for their improved feed conversion, product yield and product quality.