The reduction of emissions from diesel engines has been studied by many authors and the modification of the fuel composition is one of the most discussed proposals. In this context, the study of ab-diesel mixtures ( Alcohol + Biodiesel + DIESEL) has attracted attention due to some of its characteristics, such as combustion heat similar to that of "pure'' diesel and reduction in the emission of particulate matter and toxic gases. The presence of the paraffinic compounds in diesel hampers the solubility of polar compounds, such as alcohols, for this reason biodiesel has been studied as an agent able to solubilize the alcohol in diesel and ensure the formulation of stable mixtures. The solubility of the systems of methanol + methylic soybean biodiesel + diesel and ethanol + ethylic soybean biodiesel + diesel was studied through the construction of liquid-liquid equilibrium curves for two temperatures and it was observed that increasing temperature always increases the solubility of the components. As expected, systems using ethanol show a large homogeneous region, when compared with methanol, due to higher solubility of ethanol in diesel. The knowledge of physical-chemical properties is essential for the formulation of a fuel with characteristics within specifications. For this reason, density and viscosity data were determined for the pure/pseudo-pure components and pseudo-binary and pseudo-ternary mixtures at several temperatures and compositions. Temperature and alcohol content of the blends of alcohol + biodiesel + diesel were recognized as a major factor governing physical stability. Nevertheless, flash point was mainly dominated by the concentration of alcohol. (C) 2013 Elsevier Ltd. All rights reserved.