The aim of the present study is to test the ability of a low-cost and portable middle infrared spectrometer based on a linear array of 1 x 128 of PbSe, coupled with a linear variable optical filter in the wavelength range of 3-4.5 mu m, for the differentiation of pure chemical substances and quality control of fuels. Potential additives and adulterants for gasoline were tested, considering the alcohols ethanol, n-butanol, n-propanol and n-hexanol as potential additives and methanol and diesel oils as adulterants. Multivariate analysis of variance (MANOVA) applied to the scores obtained in the Principal Component Analysis (PCA) was conducted to analyze the spectral data and distinguish between the individual components. For the purposes of classifying anonymous samples, the centroid of each pure substance in the canonical variables was calculated, followed by the distance calculated between new samples to such centroids, assigning the individual to the most proximate category. The results demonstrated that the technique was able to discriminate between gasoline, diesel oils and the alcohols methanol, ethanol, n-propanol, n-butanol and n-hexanol and that it had the potential to be applied in the fuel industry.