In the exhaust gas fuel-reforming method, part of the engine exhaust gas reacts With small amounts of engine fuel in a mini-reactor fitted in the exhaust gas recirculation (EGR) loop to produce gaseous fuel named reformed EGR (REGR). In this study, hot REGR (gas containing H-2, CO, CH4, and CO2) was fed back to the engine inlet, so that the diesel engine in effect operated ill dual fuel with inlet heating and EGR (CO2 existence). I-lie effects of the diesel engine dual fueling with different REGR percentages oil the engine performance and emissions have been examined. The Study focused at low-load engine operation, where the conditions are not favorable for efficient gaseous fuel oxidation and engine combustion stability. The addition of the premixed gaseous fuel resulted in a remarkable reduction of both NO, and smoke engine emissions. Carbon monoxide and hydrogen oxidation efficiency call be improved by careful selection of REGR addition (e.g., premixed air/fuel ratio, inlet temperature, and reduced in-cylinder O-2 concentration) and in-cylinder diesel injection timing. The use of Pt supported on Al2O3 as an oxidation catalyst at the engine exhaust call eliminate both CO and H-2 at temperatures lower than the engine exhaust gas temperature at part loads. Preferably, in an actual engine reformer system, the uncombusted CO and H-2 will be used to enhance the after treatment system (i.e., diesel particulate filter, NOx traps, and hydrocarbon-selective catalytic reduction of NOx) performance.