The performance of Pt catalysts supported on sulfated zirconia-silica with different stoichiometries is investigated in the n-pentane hydroisomerization reaction. Comparatively, with respect to the Pt/SO42--SiO2 or Pt/SO42--ZrO2 catalysts, the sulfated mixed oxides show an enhancement of the catalytic activity that increases with the content of ZrO2, reaching its maximum at values between 10 and 15 wt% zirconia. The characterization of the samples reveals that at this stoichiometry occurs the highest H-2-consumption of the samples as well as the top value of strong Bronsted acid sites according to the TPD-H-2 and FTIR measurements of absorbed pyridine respectively. That is, close to these percents of zirconia content one has a compound that is homogeneously mixed and above those values the segregations of the single oxides occur as verified by X-ray diffraction characterization.