This work presents liquid liquid equilibrium data for systems of interest in biodiesel production, composed of Jatropha curcas oil (1) + oleic acid (2) + ethanol (3) + water (4), at temperatures ranging from (288.15 to 318.15) K and with water mass fractions in the solvent (ethanol + water) of (0.00, 2.00, and 4.00) %. The experimental data were correlated using the nonrandom two-liquid (NRTL) model, and for all systems, the global deviations between calculated and experimental data were lower than 0.96 %, showing the good descriptive quality of the NRTL model. To verify the effect of temperature (7), the water mass fraction of the solvent (w(4s)), and the fatty acid mass fraction in the oil phase (w(2)(OP)) on the distribution coefficient of the oleic acid (k(2)), a complete second-order model was fitted with a determination coefficient value higher than 0.9. The results showed that the oleic acid distribution coefficient was more affected by water content in the solvent than by temperature. Moreover, as a result of the reductions in temperature and water mass fraction in the alcoholic solvent, greater oleic acid distribution coefficients were found.