A 'smart' fuel whose molecular structure can be adapted via irradiation with light in the presence of air was calculated to provide control over ignition timing in a Homogeneous Charge Compression Ignition (HCCI) engine. The fuel consisted of isopropanol that was partially reacted into propane peroxide during a photochemical reaction with air, prior to combustion. The ensuing combustion of fuel with air in the engine, was simulated using zero-dimensional homogeneous gas phase chemical kinetic calculations. The calculations indicated that ignition timing could be controlled via the preliminary photochemical reaction. This was attributed to the presence of varying proportions of propane peroxide molecules within the fuel, which were responsible for the formation of methyl peroxy radicals early during the engine cycle. The methyl peroxy radicals increased the formation of hydrogen peroxide and hydroxy radicals during the induction period, which accelerated the decomposition reactions of the fuel, and triggered the high-temperature ignition of the fuel and air mixture. (C) 2015 Elsevier Ltd. All rights reserved.