The catalytic behaviour of the molybdenum oxycarbide catalyst, synthesized in situ from molybdenum oxide, is compared with that of a supported bifunctional platinum catalyst for the isomerization of n-octane. The main products are the mono- and di-methyl isomers, and almost no aromatics are observed. It is shown that a high selectivity to the isomer products(> 90%) can be obtained over the molybdenum catalyst, even close to the thermodynamic equilibrium (i.e., at high conversion (75%)), while this is not possible over the platinum catalyst. Furthermore, the high resistance of the molybdenum catalyst to sulphur and nitrogen catalyst poisons typically found in crude oil is shown, and the isomerization of n-heptane over a supported molybdenum oxycarbide (MoO3/SiC) catalyst is demonstrated.