Upon an innovative compact design, extraordinary heat retention capability is demonstrated with a reverse-flow catalytic converter (RFC). By periodical flow reversal, the monolith solid to gas-flow thermal energy recovery, which generates a superior temperature profile oscillating along the monolith flow-path, escalates the temperature-rise by the exothermic reaction of THC and CO. Thus, the averaged temperature level of the catalytic monolith is raised substantially independent of the inflow gas temperature from engine exhaust, while an ordinary flow-through catalyst would lose light off following similar operations with low exhaust temperatures.Along the exhaust flow-path of a typical diesel-dual fuel RFC operation, the monolith center temperature is highly elevated from the boundary temperatures, while the boundary temperatures are approximating the inflow exhaust temperature. Extensive tests conclude that CO and reactive HC conversion rates are above 95% and CH4 conversion is around 90% for most testing conditions. The RFC approach broke through the barrier of low methane conversion at low engine exhaust temperature, without utilizing external heating sources. Such a diesel dual fuel system shows low emission results following standard automotive emission testing procedures.