An oil recovery composition of an aqueous solution of one or more salts and dilute polymer and processes for enhanced oil recovery using the oil recovery composition are provided. An oil recovery composition may include an aqueous solution of one or more salts having a salinity of about 4000 parts-per-million (ppm) total dissolved solids (TDS) to about 8000 ppm TDS, a polymer having a concentration of 250 ppm to 500 ppm, metal oxide nanoparticles of up to 0.1 weight (wt) %, and dissolved CO2. The one or more salts may include at least one of sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), sodium sulfate (Na2SO4) and magnesium sulfate (MgSO4). The polymer may include a copolymer of acrylamide and acrylamido tertiary butyl sulfonate (ATBS). The oil recovery compositions provided may be suited for enhancing oil recovery in carbonate reservoirs having in situ oil viscosities less than 3 centipoise (cP).