Heterogeneous catalytic gas liquid reactions are intensified when carried out in the homogeneous fluid phase by means of a supercritical cosolvent. For instance, supercritical propane is used to enhance the yield in hydrogenation of vegetable oils. Besides phase equilibrium knowledge, volumetric information is also needed to elucidate kinetic mechanisms and design continuous supercritical reactors. In this work, we report new experimental PvT data on the reactive mixture H-2 + sunflower oil + propane using the isochoric method. In addition, the phase equilibria and PvT data are modeled with the GCA and RK-PR equations of state, respectively. The isochoric method provides not only PvT information under the reaction conditions but also the reactive system compressibility, which is a key variable to attain enhanced transport properties in supercritical reactors.