Methods of determining molecular oxygen in liquid hydrocarbon fuels are comparatively evaluated. The proposed gas-chromatographic method is based on use of a cryogenic capillary trap for preliminary separation of gaseous contaminants of oxygen, argon, and nitrogen from gasoline vapors, separation of these contaminants into oxygen together with argon and nitrogen in the analytical column of the chromatograph, measurement of the total volume fraction of oxygen and argon with a thermal-conductivity detector, and calculation of the volume fraction of oxygen with introduction of a correction that accounts for the fraction of argon in the overall total with oxygen.