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Combinatory flooding techniques evolved over the years to mitigate various limitations associated with unitary flooding techniques and to enhance their performance as well. This study investigates the potential of a combination of 1-hexadecyl-3-methyl imidazolium bromide (C₁₆mimBr) and monoethanolamine (ETA) as an alkali–surfactant (AS) formulation for enhanced oil recovery. The study is conducted comparative to a conventional combination of cetyltrimethylammonium bromide (CTAB) and sodium metaborate (NaBO₂). The study confirmed that C₁₆mimBr and CTAB have similar aggregation behaviors and surface activities. The ETA–C₁₆mimBr system proved to be compatible with brine containing an appreciable concentration of divalent cations. Studies on interfacial properties showed that the ETA–C₁₆mimBr system exhibited an improved IFT reduction capability better than the NaBO₂–CTAB system, attaining an ultra-low IFT of 7.6 × 10⁻³ mN/m. The IFT reduction performance of the ETA–C₁₆mimBr system was improved in the presence of salt, attaining an ultra-low IFT of 2.3 × 10⁻³ mN/m. The system also maintained an ultra-low IFT even in high salinity conditions of 15 wt% NaCl concentration. Synergism was evident for the ETA–C₁₆mimBr system also in altering the carbonate rock surface, while the wetting power of CTAB was not improved by the addition of NaBO₂. Both the ETA–C₁₆mimBr and NaBO₂–CTAB systems proved to form stable emulsions even at elevated temperatures. This study, therefore, reveals that a combination of surface-active ionic liquid and organic alkali has excellent potential in enhancing the oil recovery in carbonate reservoirs at high salinity, high-temperature conditions in carbonate formations.