Excess molar enthalpies, measured at the temperature 298.15 K in a flow microcalorimeter, are reported for the ternary mixtures {x(1)CH(3)CH(2)OC(CH3)(3) + x(2)CH(3)(CH2)(4)CH3+ (1-x(1)-x(2))CH3(CH2)(5)CH3} and x(1)CH(3)CH(2)OC(CH3)(3) + x(2)CH(3)(CH2)(4)CH3 + (1 - x(1) - x(2))CH3 (CH2)(6)CH3}. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the enthalpies of the ternary mixtures can be obtained from the Liebermann and Fried model, using only the physical properties of the components and their binary mixtures.