The depletion of dissolved O-2 has been measured at 185 degrees C for a series of 12 jet fuels diluted 10-fold in a paraffinic solvent. Reaction is limited by the fixed amount of O-2 present in air-saturated fuel. Because of dilution, aromatics, olefins, and also species such as dissolved metals and natural secondary antioxidants that influence oxidation by collision with hydroperoxides are less important. Under such dilute conditions, autoxidation is simplified, being governed mainly by the residual natural primary antioxidants acting as retarders or inhibitors to slow oxidation of the diluent. Oxidation of diluted fuels is, therefore, characterized by a time delay, followed by reaction acceleration. The time required to achieve 50% conversion of O-2 has been used as a measure of the efficiency and concentration of primary antioxidants present in the diluted fuel. In turn, it is proposed that this time is an indirect measure of primary antioxidants originally present in the neat fuel. Similarity in the observed oxidation behavior of diluted fuels and hydrotreated fuels and the parallel of removing polar species either by dilution or by hydrotreatment lead to classification of such diluted fuels as surrogate hydrotreated fuels. Improved thermal stability following dilution, differences in the response of the neat and the diluted fuel to several additives, the effect of increased inital dissolved O-2, and the measured concentration of hydroperoxides further support the analogy between dilution and hydrotreatment.