Rates of molecular oxygen consumption at 23°C and 1 atm O2by a coal-derived middle distillate containing cyclohexanol and other additives are reported. Significant inhibition of fuel oxidation was observed in the presence of 0.15% w/w benzylidene benzoylhydrazine, HBBz, but was not observed if the fuel had first been treated with pentane to precipitate gum and the predominant metals. Gum precipitated in the presence of HBBz had a higher S content than in its absence. Equilibria between HBBz, metals in the fuel and catalyst X (which may contain sulfur) are suggested to account for inhibition of fuel oxidation by HBBz.