We have tested typical samples of fuel (diesel, gasoline, technical gasoline and a mixture of unknown fuel). For fuel analysis we have used an analyzer IROX DIESE with an in-built infrared interferometer of Michelson’s type. The results proved that within a wavemeter from 650 up to 1800 cm-1 for each fuel there is a typical infrared spectrum. This spectrum can be compared with human fingerprints. It is possible to positively identify the majority of fuels with the usage of these spectra. Moreover in case of unknown mixture, it is possible to use these spectra for determination of their mutual ratio.