A microkinetics simulation method, developed to analyze the kinetics of the hydroisomerization of n-hexane, was used to clarify the cause of the temperature dependency of the Arrhenius activation energy of the hydroisomerization of short alkanes on a Pt/mordenite catalyst. It was shown that the model reproduces experimental data. Parameters have not been adjusted, but originate from independent experiments. The change toward lower activation energies at higher temperatures is shown to be due to a decrease in the surface coverage of the active intermediate. This results in a change in the reaction order. The simulations prove that in the temperature regime considered neither intracrystalline diffusion nor single file diffusion or a change in the rate-determining step is needed to explain the temperature dependence of hydroisomerization over Pt/mordenite catalysts, The measured activation energy changes from the true activation energy for hydroisomerization when site coverage is high to the true activation energy minus the adsorption enthalpy of the reactant at low coverage.