Experimental and modeling results for dilute stoichiometric oxidation of isooctane in the intermediate temperature regime are presented for pressures of 6 and 9 atmospheres. While the overall comparison between the experiments and modeling is acceptable, important differences exist in the predictions of the mole fractions of acetone and methacrolein, which are products of isobutene oxidation. The results from this study are compared to earlier work on the oxidation iso-octane under very lean conditions to illustrate the significance of chemical pathways in which molecular oxygen is a key reactant.