A process for producing a high RON naphtha which comprises contacting a hydrocarbon feed stream comprising a mixture of the isomers of C₅ and C₆ paraffins with ATS zeolite, such as SSZ-55, in an adsorption zone, whereby the branched isomers of the C₅ and C₆ paraffins are preferentially adsorbed by the ATS zeolite as compared to the straight chain isomers, and recovering a naphtha product from the adsorption zone having a higher RON than the hydrocarbon feed stream, also including a hydroisomerization process and a hydrocracking process.