Octane was considered to be a potential entrainer for the recovery of spent sulfuric acid by heterogeneous azeotropic distillation. The vapor-liquid equilibria (VLE) data were determined for octane + ethanol, octane +, water + ethanol, and octane + sulfuric acid + water + ethanol systems at (30, 60, 90, and 101.3) kPa using the ebulliometric method. The VLE data were used to regress the electrolyte nonramdom two-liquid interaction parameters with the help of Aspen Plus for pairs: C8H18-C2H6O, C8H18-H2O, H2SO4-C2H6O, C2H6O-[H3O](+):[HSO4](-), C2H6O-[H3O](+):[SO4](2-), C8H18-[H3O](+):[HSO4](-), and C8H18-[H3O](+):[SO4](2)-. The correlation fitted the experimental data well for all the systems. The maximum absolute deviation and average absolute deviation for temperature for the systems are 0.86 K and 0.26 K, respectively.