New dynamic viscosity data are reported for binary mixtures of ionic liquid 1-hexyl-3-methylimidazolium tetrafluoroborate, [C(6)mim]-[BF4], with polar aprotic solvents dimethyl sulfoxide (DMSO) and acetonitrile (ACN) over the whole composition range at experimental pressure p = 0.1 MPa. The temperature dependence of viscosity was studied in the T = (293.15 to 353.15) K temperature range. The viscosity data for binaries have been correlated with models based on Eyring's absolute rate theory with one, two, and three parameters and also with the classical equations of Grunberg-Nissan and McAllister. We also analyzed the capacity of the group contribution methods recently proposed by Zhao and Jacquemin for predicting the viscosity of binary mixtures with ILs. The results we obtained were promising, especially at lower temperatures, where the relative deviations, AAD%, were about 5 to 6%. The deviations in viscosity were calculated and correlated by a fourth-order Redlich-Kister type equation. The results were discussed in terms of interactions and interstitial accommodation between components in the binary mixtures.