Diesel, inside all energy matrixes, is considered a valuable resource. Brazilian S-10 diesel can be subject to adulteration by addition of residual automotive lubricant (RAL), to increase the profit margin for distributors and fuel service stations. The use of mid-infrared (MIR) spectroscopy in combination with multivariate calibration methods as a quantitative analytical method can provide satisfactory results in accordance with those found using conventional methods. We report the use of MIR spectroscopy and multivariate calibration using the partial least squares method (PLS) for the quantitative analysis of RAL as an adulterant in Brazilian S-10 diesel. Our results displayed good correlation between the reference values and those calculated using the PLS model with low error values. The model was built in accordance with standard method ASTM E1655-05 and validations of the figures of merit were estimated. (C) 2014 Elsevier Ltd. All rights reserved.