Process for upgrading hydrocarbon fuels

Hydrocarbon fuels, for example straight run gasoline and cat-cracked spirit, are up-graded by reacting the fuel with a hydrocarbyl hydroperoxide at a temperature greater than the decomposition temperature of the hydroperoxide and at a pressure sufficient to maintain the reactants in the liquid phase. The reaction may be carried out in the presence or absence of a metal catalyst for the decomposition of the hydroperoxide and optionally in the presence of a solid not generally regarded as a hydroperoxide decomposition catalyst, e.g. alumina, silica or silica-alumna.