This paper is a continuation of our systematic investigations on piperidinium ionic liquids and presents new data on activity coefficients at infinite dilution for 43 solutes: linear and branched alkanes, cycloalkanes, alkenes, alkynes, benzene, alkylbenzenes, alcohols, water, thiophene, tetrahyrdofuran (THF), methyl tert-butyl ether (MTBE), linear ethers, acetone, and linear ketones in the ionic liquid 1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide, [BMPIP][NTf(2)]. The data were determined by gas liquid chromatography (GLC) at temperatures from 308.15 to 358.15 K. These values were compared to those previously published for the bis(trifluoromethylsulfonyl)imide-based ionic liquids. The partial molar excess enthalpies Delta H(1)(E,infinity) and entropies Delta S(1)(E,infinity) at infinite dilution were calculated from the experimental gamma(infinity)(13) values obtained over the temperature range. The values of the selectivities for different separation problems were calculated from gamma(infinity)(13) and compared to literature values for N-methyl-2-pyrrolidinone (NMP), sulfolane, and additional ionic liquids. Experimental limiting activity coefficients were used to calculate gas-IL partition coefficients of solutes, K(L). The modeling with specific linear solvation energy relationship (LSER) equations was performed for data obtained in this work and those reported earlier for 1-butyl-1-methylpiperidinium thiocyanate, [BMPIP][SCN].