Infrared (IR) is the spectroscopic technique most extensively applied in the industry because it has a low cost, good signal-to-noise ratio, rapid response potential for online applications, non-destructive and non-invasive instrumentation, and simple or nearly no specific sample preparation. In consequence, IR has been extensively used in the characterization and classification of different crude oils (medium and heavy), gasoline, and associated products that have been carried out with this technique that is based on the characteristic vibrational modes of the functional groups present in the sample. NIR has been used in the oil and gas industry since the late 1970s and early 1980s. Many applications appeared that demonstrate the success of near-infrared (NIR) for the prediction of physical and chemical properties of crude oil and petroleum products. "Chemometrics" is a term applied to the generic discipline containing computers and mathematics to derive meaningful chemical information from samples of varying complexity.