This paper presents new methodology of ignition property measurements using a micro flow reactor with a controlled temperature profile, which is a spin-off methodology developed through microcombustion studies during the last decade. Stable multi-stage reaction zones were observed in low flow velocity regime for hydrocarbons and it was found that unsteady multi-stage oxidations of hydrocarbons were examined by stable multi-stage reaction zones termed as weak flames. This methodology has been further applied to various fuels. Effects of research octane number of primary reference fuels on weak flames were examined and it was shown that stabilized temperature levels and appearances of weak flames have apparent correlations with RON. Recent works using the micro flow reactor were also introduced.