For understanding flame stability in microcombustor, fundamental studies on the combustion characteristics in a meso-scale channel with a prescribed wall temperature profile have been conducted. Results showed that the existence of dynamic oscillatory flames and weak flames in addition to the normal propagating flames for the first time. It is then recognized that the weak flame phenomena can be applied for examining multi-stage oxidation of hydrocarbon fuels in wide temperature range from 300K up to auto-ignition temperature. Based on the preliminary experiments with various fuels including primary referenced fuel for gasoline, research octane number (RON) of the test fuels can be clearly described by the aspects of the stabilized stationary multiple weak flames. The methodology can be termed "flame chromatography" and it is expected to be applied for fuel indexing of future alternative fuel characterizations.