[BF4], the maximum conductivity was obtained at xIL,max=0.3. Rilo et al. also observed similar behavior for [EMIM] + , [BMIM] + , [HMIM] + , and [OMIM] + cationic group paired with [BF4] -anion in ethanol at xIL,max=0.54, 0.28, 0.18, and 0.18, respectively, at 298.15 K temperature. It could be observed in Rilo's study that the composition for [HMIM] + and [OMIM] + is same, which was also obtained for the present study. Interestingly, the ionic liquid mole fractions at which ionic conductivity maximum is observed are higher in ethylene glycol than those in ethanol except [EMIM][BF4]. The behavior could be attributed to a higher dielectric constant for ethylene glycol, enabling a higher dissociation of ionic liquids due to greater screening of electrostatic interactions. Furthermore, the presence of two -OH groups in ethylene glycol as opposed to one in ethanol provides more opportunities for hydrogen bonding in ethylene glycol, resulting in improved solvation of charged species. After comparing the behavior of ξr with the ionic conductivity, it could be observed that the ξr of this RTIL system showed a similar trend as ionic conductivity (Figure ). This potentially validates our hypothesis that the ion dissociation governs the observed trend of increasing conductivity with the composition of ionic liquid and reaching the maximum value at a particular composition, then approaching the ionic conductivity of neat RTIL. Therefore, ξr is a significant parameter for any RTIL system to define the dissociation of the ions in any molecular solvent. In addition, this phenomenon could also be identified as the competing effects of enhancing free ions concentration against the enhanced viscous forces hindering the diffusion of ions in the system. Therefore, viscous forces and free ions are the significant parameters that control the mobility of the ions and, thus, the ionic conductivity. It could also be observed from Eq. ( ) that the ionic conductivity is defined by the ion mobility (ui). For this purpose, the behavior of the solution viscosity (η) (calculated from Eq. ( )) and relative mobility of cations (u+,r) (calculated from Eq. ( )) of all RTILs in EG with the composition of RTILs is shown in Figure and Figure (supporting information), respectively. It could be observed from Figure (supporting information) that the viscosity of the solution of the RTIL and EG increases with the increase of the RTIL concentration from infinite dilution condition, i.e., the viscosity of the solvent, EG, to the neat RTIL viscosity. Figure (supporting information) shows that as the alkyl chain length increases, the relative mobility of the cations decreases, which could be related to the ionic conductivity behavior with alkyl chain length.