This work reports new measurements of the viscosity of liquid diethylene glycol dimethylether (DEGDME) upto 100 MPa at eight temperatures ranging from 293.15 to 353.15 K. The measurements at atmospheric pressure have been performed with an Ubbelohde-type glass capillary tube viscometer with an uncertainty of +/-1%. At pressures upto 100 MPa the viscosity was determined with a falling body viscometer with an uncertainty of +/-2%. Using previous polyalkylene glycol dimethylether viscosity and density data (Triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether) obtained at the laboratory, present measurements were used to study the dependence of the viscosity and of the molecular parameters of hard-sphere scheme and free-volume model on the number of CH2-CH2-O groups. (C) 2004 Elsevier B.V. All rights reserved.