Measurements on densities, viscosities, and refractive indices at atmospheric pressure for binary mixtures of 1,3-dimethyladamantane (1,3-DMA), 1,3,5-trimethyladamantane (1,3,5-TMA), and 1-ethyladamantane (1-EA) with n-nonane or n-undecane are carried out over the whole composition range at temperatures T = 293.15-343.15 K and atmospheric pressure. The excess molar volume (V-m(E)), deviation in viscosity (Delta eta), deviation in refractive index (Delta n(D)), and deviation in molar refraction (Delta R) for the six mixtures are calculated and then fitted to the Redlich-Kister polynomial. The V-m(E) values are all negative over the entire range of mole fractions and decrease with increasing temperature for the six binary systems. The absolute values of Delta eta for the mixtures decrease obviously with increasing temperature. The Delta n(D) values with the volume fraction for the six systems are all positive over the entire composition range. Density, viscosities, and refractive index of the six systems are correlated by the Jouyban-Acree model. The experimental results could be useful for the development of high-energy-density hydrocarbon fuels.