Conventional petroleum jet and diesel fuels, as well as alternative Fischer-Tropsch (FT) fuels and hydro-treated renewable jet (HRJ) fuels, contain high molecular weight lightly branched alkanes (i.e., methylalkanes) and straight chain alkanes (n-alkanes). Improving the combustion of these fuels in practical applications requires a fundamental understanding of large hydrocarbon combustion chemistry. This research project presents a detailed and reduced chemical kinetic mechanism for singly methylated iso-alkanes (i.e., 2-methylalkanes) ranging from C-7 to C-20. The mechanism also includes an updated version of our previously published C-8-C-16 n-alkanes model. The complete detailed mechanism contains approximately 7200 species 31400 reactions. The proposed model is validated against new experimental data from a variety of fundamental combustion devices including premixed and non-premixed flames, perfectly stirred reactors and shock tubes. This new model is used to show how the presence of a methyl branch affects important combustion properties such as laminar flame propagation, ignition, and species formation. Published by Elsevier Inc. on behalf of The Combustion Institute.