Polyoxymethylene dimethyl ethers (DMMn) have attracted particular attention in industry as excellent oxygenated fuel additives. This study aims to reveal the liquid-liquid equilibrium (LLE) values regarding ternary mixtures {water + methylal (DMM1) + 4-methyl-2-pentanol (MIBC)}, {water + DMM2 + MIBC}, {water + DMM3 + MIBC}, and {water + DMM4 + MIBC} at 298.2 and 308.2 K under 101.3 kPa. Distribution factor and selectivity were utilized to assess the extracting capabilities of the selected extractant. The well known Hand equation and Othmer-Tobias equation were utilized to test the consistency of the LLE values. In addition, the experimental results were correlated by the UNIQUAC and NRTL thermodynamic models with all of the root-mean-square deviation values less than 0.0127,which indicated that both models agree well with the experimental tie-line data.