We studied the three-phase behavior and dissolution behavior of propanol (C3OH) in a water/(CEO8)-E-12/C3OH/cyclohexane (C-C-6)/heptane (C-7) system at 35 and 45 degrees C. Without C12EO8, a three-phase region (IIIa) consisting of C3OH, aqueous (W), and oleic (O) phases exists between R-oil (c-C-6/c-C-6 + C-7) = 0.2 and 0.3 (w/w) above 35 wt% C3OH. The C3OH phase originates from the W phase and becomes identical to the O phase with increasing R-oil. In the presence of C12EO8, the three-phase region expands below 20 wt% C3OH. The surfactant phase behaves in two ways according to the role of C3OH. When R-oil < 0.2, the D-p phase forms a closed-loop miscibility gap with a W phase. The added C3OH acts as a lipophilic cosurfactant and a water-soluble cosolvent. When R-oil > 0.3, a microemulsion (D) phase changes from water-rich to oil-rich in a chiral three-phase body. Most C3OH added acts as a lipophilic cosurfactant at R-oil = 1. The two types of three-phase behavior are transformed into each other via region IIIa. C3OH cooperatively acts with C12EO8 and a higher-order phase is formed.