Experimental measurements of dew points for 14 methane + carbon dioxide + water + methanol mixtures at pressures between 1.0 X 10(5) and 59.1 x 10(5) Pa in the temperature range from 241.6 to 288.8 K were made. The experimental results obtained on the quaternary systems were analyzed in terms of a predictive EF-EOS (excess function-equation of state) method, which reproduced experimental dew-point temperature data within an AAD (absolute average deviation) of between 0.0 and 1.9 K.