The densities and viscosities for the binary systems of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim] [BF4], with the molecular solvents: dimethylsulfoxide (DMSO) and ethylene glycol (EG), were measured over the whole concentration range in the temperature range from (293.15 to 353.15) K by using an Anton Paar DMA 4500 densirneter and an Anton Paar AMVn measuring assembly, respectively. The temperature dependence of density and dynamic viscosity both for pure [Bmim] [BF4] and its binary mixtures can be described by an empirical linear equation and by the Vogel-Fucher-Tammann (VFT) equation, respectively. The excess molar volumes, V-E, were calculated by using the measured experimental data and fitted to a Redlich-Kister equation. These values are negative for the [Bmim][BF4] + DMSO system and positive for the [Brnirn][BF4] EG system over the whole composition range at investigated temperatures. The V-E results have been analyzed using the Prigogine-Flory-Patterson (PFP) theory, which can explain the volumetric behavior of the investigated binary mixtures.