The effect of key computational parameters of the quantum chemical approach underpinning the COSMO-SAC model is investigated, considering as target property the activity coefficients at infinite dilution, gamma(infinity), of furan in several solvents. In particular, different density functional theory models, as well as parameters concerning the solvent model (COSMO), are varied, and the obtained results were compared with the experimental data, integrated with specific experiments, as well as with those provided by empirical methods such as UNIFAC. The results show that a significant improvement in the COSMO-SAC evaluation of gamma(infinity) is obtained by a judicious choice of the computational parameters, including the exchange-correlational functionals and the atomic cavity radii. More importantly, the accuracy of the obtained protocol on gamma(infinity) is significantly better than that provided by the robust and widely used UNIFAC model.