Enhanced production of light olefins

In a method for forming a light olefin product by the catalytic cracking of a hydrocarbon feed that contains at least in part a mixture of heavy olefins using both a catalyst system and reaction conditions effective for the formation of light olefins, the improvement comprising, co-feeding along with said hydrocarbon feed to said catalytic cracking a minor effective amount of at least one oxygen containing hydrocarbon selected from the group consisting of alcohols, ketones, ethers, carboxylic acids, polyols, aldehydes, cyclic ethers, epoxides, and mixtures of two or more thereof, whereby aromatics and/or C8 and heavier hydrocarbons in said light olefin product are reduced in amount below what they would have been had the oxygen containing compound not been employed.