We present an equation-of-state approach to modeling the thermodynamic properties of a biodiesel fuel. Preliminary Helmholtz-type equations of state were developed with limited experimental data for live fatty acid methyl esters (FAMEs) that are the primary constituents of soy-based biodiesel fuel, namely, methyl palmitate, methyl stearate, methyl oleate, methyl linoleate, and methyl linolenate. These components Were combined in a mixture model using ideal mixing to represent the thermodynamic properties of a biodiesel fuel. We performed limited experimental measurements on the density, sound speed. and initial boiling point of two biodiesel fuel samples and compared the results with the model.