The aim of this work was to improve the performance of the liquid-liquid extraction of naphthalene froma fuel phase using amixture composition as extractant. The composition of the extractantmixture was performed by implementing an experimentalmixture designwhere themixing proportions of the three components dimethyl sulfoxide, methanol and phenol, were studied. The response was the effect of the solvent on the extraction yield of naphthalene. The results treated in a statistic way were interesting and showed that the optimumconditions can enhance the yield of extraction until 84.56 % theoretically. An experimental validation of the model in the same conditions had given a yield of 83.48%.