[en] Densities of pure 1-ethyl-3-methylimidazolium ethylsulfate ionic liquid - [C₂mim][EtSO₄] and its mixtures with methanol have been measured with an accuracy of ±0.2 kg . m^-3, over the temperature range (283.15 to 333.15) K and pressure range (0.1 to 35) MPa, using a vibrating tube densimeter. Excess volumes have been calculated directly from the experimental densities. The latter data have been correlated by the Tait equation with the temperature dependent parameters for the pure ionic liquid and by a van Laar-type equation, involving parameters dependent on temperature and pressure for the mixtures. The isobaric expansivity, isothermal compressibility, and related excess properties have been calculated. The exceptionally strong influence of pressure and temperature on these properties has been observed