Excess molar enthalpies of {x(1) tert-butyl methyl ether (MTBE) + x(2) 1-pentanol+ (1 - x(1) - x(2))decane} and the involved binary mixtures {x tert-butyl methyl ether (MTBE) + (1 - x)decane} and {x 1-pentanol+ (1 - x)decane} have been determined at 298.15 K and atmospheric pressure over the whole composition range using a Calvet microcalorimeter. The results were fit by means of different variable-degree polynomials. In the present work, we propose a new expression to fit the ternary excess molar enthalpy, which takes into account the asymmetric shape of the involved binary systems. The group contribution model of the UNIFAC (in the versions of Larsen and Gmehling) were used to estimate excess enthalpy values. Several empirical expressions for estimating ternary properties from binary results were also tested.