An infinite-dilution activity coefficient model for predicting the SLE of a binary system consisting of a long-carbon-chain alkane solute (j) and a short-carbon-chain alkane solvent (i) has been investigated using SLE data satisfying the Gibbs-Duhem equation. It has been demonstrated that the temperature dependency of heat capacities of a solute alkane has a strong effect on the infinite-dilution activity coefficient of the solute, ln γ(∞)(j). The criteria for the establishment of infinite-dilution for the alkane/alkane SLE have been proposed. Infinite-dilution Wilson parameters introduced in the residual term of ln γ(∞)(j) have been determined from the regression using the SLE data. The Wohl equation combined with the present model accurately predicts the solubilities of the solute alkanes, while conventional models less satisfactorily predict the solubility. The ordered structure formed in a short-chain carbon solvent alkane liquid is partly destroyed, leaving the strength of molecular interactions unchanged when a molecule of an alkane having a longer carbon chain is introduced into the solvent alkane.