Measurements of excess molar enthalpies at the temperature 298.15 K are reported for the ternary mixtures {x(1)C(2)H(5)C(CH3)(2)OCH3 + x(2)CH(3)(CH2)(4)CH3 + (1 - x(1) - x(2))CH3(CH2)(v-2)CH3} with v = 10 and 12. Smooth representations of the results are presented and used to construct constant-enthalpy contours on Roozeboom diagrams. Comparisons of the experimental results with estimates based on the Flory theory of mixtures are also described.