A petroleum recovery method employing a mixed solvent for use in subterranean petroleum-containing formations. The mixed solvent density is less than the density of water and greater than the density of the formation petroleum, and preferably has a boiling point less than the boiling point of the formation petroleum. Water is injected into the bottom of the petroleum formation and solvent is injected into the formation above the depth at which water is injected, and a mixture comprising solvent and petroleum is recovered from production wells. The solvent may be separated from the produced petroleum-solvent mixture by distillation and recondensation for reinjection into the formation. The rate of water injection is controlled to force the horizontally moving solvent bank slowly upward so as to sweep the entire formation.