Hydrogenation is frequently performed at conditions that lead to the skeletal isomerization of the product. Polymer gasolines from SPA catalysts are highly branched, much more than predicted from thermodynamic equilibrium. Therefore, skeletal isomerization of these products would tend to move in the direction to equilibrium and, thus, to less branched products and to lower octane numbers. Thus, in general, hydrogenation catalysts that avoid isomerization should be selected.