Thermal cracking experiments were carried out to promote the conversion of waste cooking oil into a biofuel which is similar to gasoline (light-naphtha). Temperature and residence time were varied in order to analyze their effects on the light-naphtha characteristics in terms of acid value and chemical composition, (paraffins, i-paraffins, olefins, naphthenes, oxygenates and aromatics). The PIONA analysis was used to determine the composition of chemical groups in the light naphtha obtained and its benzene concentration. The results show that at higher temperatures and with longer residence times the benzene concentration increases, but the values obtained are close to the limits of the regulatory specifications of European and Brazilian laws. (c) 2012 Elsevier Ltd. All rights reserved.