The oxidation of diesel hydrocarbons over platinum supported on mesoporous silica doped with secondary component metals (Al, Zr, Ti, Ce, La, Ca, Mg) via a sol–gel technique was investigated. Pt/SiO2 had the lowest oxidation activity, exhibiting a conversion of only 75 % at 500 °C. In all cases, the catalytic activity of this material was significantly improved by doping with a secondary component metal. The observed order of improvement by metal, from highest to lowest, was: Al, Zr, Ti, La, Ca, Mg, Ce. Pt/Al–SiO2 and Pt/Zr–SiO2 in particular showed high activity with T 50 values of 203 and 220 °C, respectively. The materials with greater platinum dispersion and with more acidic sites exhibited higher activity. The effects of varying Zr content in the Pt/Zr–SiO2 catalyst were also investigated. Both platinum dispersion and the number of acidic sites were increased with increasing Zr content and catalytic activity was significantly improved, reaching a maximum at approximately 5 mol % Zr.