The simplicity, reliability and cost-effectiveness of ejector-based technologies have paved way to recover low-pressure gases which are normally flared by the oil companies. In this study, a numerical analysis was performed to evaluate the performance of an ejector for flare gas recovery application. Initially water was used as the primary fluid and air as the secondary fluid. The analysis was then extended to different combinations of primary and secondary fluids, namely, water–methane, crude oil–air and crude oil–methane, respectively. The governing equations of fluid flow were solved for both liquid and gas phases. The entrainment and pressure ratio varied as the design parameters and operating conditions were changed. The role of setback distance on the location of jet breakup was presented. Primary flow rate optimization was done to find the maximum flow rate for the design as the best performance can be obtained at that flow rate. The optimum setback distance and the flow rate of the primary fluid were found to be 34 mm and 0.76 lps, respectively. The role of primary fluid viscosity and suction fluid density was also presented. A maximum efficiency of 44% was observed when crude oil was used as the motive fluid for recovery of these gases. © 2014 Taylor & Francis.