This paper reports on the performance of several ionic liquids for use in separating an olefin (1-octene) from a paraffin (n-octane). To quantify the effectiveness of an ionic liquid in a given separation, a measurement of the activity coefficients of the solutes in the solvent can be used as a guide. This measurement permits the calculation of selectivities and capacities that are important factors in judging the suitability and potential commercial viability of an ionic liquid for a separation application. Several different ionic liquids were tested and compared to a traditional, conventional solvent, N-methyl-pyrrolidone (NMP), and to each other. One ionic liquid tested, silver(I)/N,N-dimethylbenzoamide bis(trifluoromethylsulfonyl) imide [Ag(DMBA)2 +Tf2N−], showed selectivities 24−32 times higher than NMP while maintaining a comparable mass capacity as the nonionic solvent. The experimental data showed that this particular ionic liquid was also superior to any of the other ionic liquids tested in this series of experiments. This ionic liquid has the potential to be used in an economically viable commercial process to recover valuable olefinic components from streams where they are mixed with paraffins.