Refractive indices were measured over the entire composition range at atmospheric pressure for the binary mixtures CH3OH with CH3OCH2(CH2OCH2)(3)CH2OCH3 (2,5,8,11,14 pentaoxapentadecane, or Tegdme) and CH3OCH2(CH2OCH2)(n)CH2OCH3 (n = 3-9) (Pegdme 250) at temperatures from 293.15 K to 333.15 K. The experimental values were fitted by a polynomial equation in mole fraction. Experimental values were measured with an Abbemat-type refractometer with a synthetic sapphire prism (sodium D wavelength). Changes of refractive index on mixing were determined and fitted to a variable-degree polynomial equation. Their parameters and root-mean-square deviations were calculated.