Environmental issues, the growing demand for energy, political concerns, increasing crude oil prices and the medium-term depletion of petroleum created the need for the development of vegetable oils as alternative fuels. Vegetable oil-based fuels (bio fuels) are promising alternative fuels for diesel engines because of their environmental and strategic advantages. To design equipment for biofuel production and an optimizing process for biodiesel production, their thermophysical properties must be known. In this work, the Jatropha curcas biodiesel was prepared, and thermophysical properties, densities (rho(12)), and speed of sound (u(12)) for J. curcas biodiesel (1) + diesel fuel no 2 (2) binary mixtures were measured as functions of composition at temperatures ranging from T = (288.15 to 308.15) K and atmospheric pressure. The observed data have been utilized to evaluate the excess molar volume, V-12(E), of this binary mixture. This binary mixture (blend) exhibits a temperature-dependent behavior, and densities decrease linearly with temperature.