Thermal diffusivity measurements of different oils and their respective biodiesels are investigated by means of thermal lens spectroscopy. The viscosities of biodiesel decrease by approximately one order of magnitude, while thermal diffusivity showed an inversely proportional dependence with respect to the produced biodiesels from several oils sources. This correlates to unsaturation levels present in the fatty acid chains according to the iodine index value for each one. In addition, a reduction of the Prandtl number of biodiesels by around an order of magnitude relative to their corresponding oils was observed as consequence of the viscosity reduction. The results of this work will facilitate physicochemical and thermophysical property collection for biofuels and will be relevant for mathematical modeling and numerical simulation studies related to combustion of diesel/biodiesel blends and pure biodiesel. (C) 2014 Elsevier Ltd. All rights reserved.