Due to the environmental problems caused by the CFCs, there, is a growing interest in the use of absorption cycles. Organic working pairs using polyethylene glycol dimethyl ether 250 {CH3OCH2(CH2OCH2)(n)CH2OCH3}, where n = 3-9 as absorbent have been proposed to overcome the drawbacks of classical working pairs as (NH3 + H2O) and (LiBr + H2O). For a better knowledge of this type of mixture, reliable data of diverse thermophysical properties such as the relative permittivity are required. Therefore, an experimental study of the relative permittivity has been continued for (methanol + polyethylene glycol dimethyl ether 250), also denominated Pegdme 250. The measurements were determined at atmospheric pressure in the temperature range of 283.15-323.15 K over the whole composition range using a HP4284A precision LCR Meter at frequency 1 MHz. From the experimental values, the corresponding increments were determined and fitted to a variable-degree polynomial equation. Furthermore, we have evaluated the predictive capacity of some estimation methods, so that the comparison of the predictions with the results obtained experimentally is made. Those methods have been applied in the case of volume change on mixing and. under the supposition of volume additivity. In general, for all temperatures, it is observed that the estimates obtained are better in the case of volume change on mixing.