Vapor-liquid equilibrium (VLE) data are reported for the binary mixtures formed by octane and the branched ether 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME). A Gibbs-van Ness type apparatus was used to obtain total vapor pressure measurements as a function of composition at 298.15, 308.15, 318.15 and 328.15 K. The system shows positive deviations from Raoult's law. These VLE data are analyzed together with data previously reported for octane + TAME mixtures: VLE data at 323.15 and 423.15 K, excess enthalpy (H-m(E)) data at 298.15 and 313.15 K and excess volume (V-m(E)) data at 298.15 K. The UNIQUAC model, the lattice-fluid (U) model, and the Flory theory are used to simultaneously con-elate VLE and H-m(E) data. The two latter models are then used to predict 11 V-m(E) data. The original UNIFAC group contribution model and the modified UNIFAC (Dortmund model) are used to predict VILE data.