The biodiesel blended with aqueous ethanol and diesel was successfully prepared to employ a near isochoric subcritical in which methyl esters were derived from coconut oils. Procedures are as follows: Fermentation of Arenga pinnata sap, a distillation of ethanol using a reflux column, preparation of biodiesel, characterization of biodiesel by GC/MS, blending of aqueous ethanol-biodiesel and aqueous ethanol-dieselbiodiesel, measurement of composition, and analysis of fuel parameters with ASTM standard. The maximum yields of biodiesel obtained were 98.82%(v/v) and 96.67%(w/w). The coconut oil methyl esters (COME) degraded from triglycerides were dominated by the short carbon chains, such as C9H18O2, C11H22O2, C13H26O2, C15H30O2, and C17H34O2. It was found that the aqueous ethanol-biodiesel and aqueous ethanol-biodieseldiesel formed an equilibrium line in a triangular graph in specific compositions. The aqueous ethanol concentrations using in the present work were 94-97%. Components pure ethanol-biodiesel-water, which were in the stable blends, had a range of 13.16-33.95, 65.00–86.00, and 0.84–1.05%. Meanwhile, the blends aqueous ethanol-diesel-biodiesel were 7.45–21.88, 10.64–25.97, and 56.25–81.91%, respectively. It was discovered that droplets appeared in solution when using ethanol with purity below 95% but were distributed uniformly. The addition of biodiesel continually after a stable emulsion formed, the phase separation would not have occurred.