The soluble macromolecular oxidatively reactive species (SMORS) mechanism has recently been applied to jet fuel thermal oxidative degradation at high temperatures (250-550 degrees C). The primary purpose of this work is to further test the extant SMORS mechanism with carefully designed experiments at lower temperatures. First, synthetic SMORS precursors, 2-methylindole and 1,4-benzoquinone, were doped into a stable Jet A-1 in both mono- and oligomeric forms. Flask oxidative stress of these solutions at 90 degrees C for 60 min with an oxygen sparge significantly increases jet 41 thermal oxidative degradation. Second, a model compound experiment suggests SMORS precursors, phenol and 1,4-benzoquinone, are generated in situ from flask oxidation of a natural jet fuel component cumene (isopropylbezene) at 160 degrees C with an air sparge for 300 min. This observation is particularly significant for the thermal oxidative degradation of ultra-low sulfur diesel (ULSD) be use it suggests that fuels with low heteroatom content may oxidatively degrade by the SMORS mechanism. Third, doping parts per million (ppm) levels of 2,4-dimethylpyrrole into oxidatively stable jet fuels followed by flask oxidation at 95 degrees C with an air sparge for 30 min results in significant oxidation of the jet fuels. This observation is particularly significant for the storage and thermal oxidative stability of Athabasca-tar-sands-derived middle distillates, which have previously been shown to contain alkylpyrroles; these middle distillates are predominate across the northern tier of the United States.