In this study, measurements regarding the density and speed of sound for binary liquid mixtures of the 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid (+ methanol, or + acetonitrile, or + tetrahydrofuran, or + formamide, or + N,N-dimethylformamide, or + dimethylsulfoxide) were carried out as a function of the composition at temperatures between 288.15 and 313.15 K and atmospheric pressure. Experimental results allowed us to calculate the excess molar volume, V-m(E), and excess isentropic compressibility, kappa(E)(s), which were fit to a Myers-Scott-type polynomial. The results for the studied systems suggest that structural effects and chemical interactions must predominate over other possible effects, except for the system containing formamide in which physical effects may also be more important.