A process for economically converting carbo-metallic oils to lighter products. The carbo-metallic oils contain 650.degree. F.+ material which is characterized by containing material which will not boil below about 1025.degree. F., a carbon residue on pyrolysis of at least about 2, and a nickel plus vanadium content of at least about 4 parts per million. This process comprises adding an additive to the feedstock consisting of a compound containing titanium, zirconium, or aluminum so as to restore cracking activity of high metal contaminated and deactivated, zeolite containing catalysts, resulting from processing of these carbo-metallic oils.