The viscosities of the gas expanded liquid system of methanol with carbon dioxide were experimentally determined with a recently developed method of falling-weight viscometry. Carbon dioxide concentrations within the gas expanded liquid system were systematically increased by the addition of carbon dioxide into an isochoric system containing metered amounts of methanol. New experimental viscosity data for the expanded liquid phase of methanol with carbon dioxide are presented at 25, 30, 35 and 40 degrees C and at mole fractions of carbon dioxide in the liquid phase between 0.10 and 0.85 in 0.05 increments along all four isotherms. The apparent correlating factor for deducing the viscosity of carbon dioxide expanded methanol appears to be the composition of the liquid phase and the degree of volume expansion of the liquid phase, as opposed to liquid density and system pressure values. Viscosity reduction is almost linear up to about 0.5 mole fraction carbon dioxide before the rate of viscosity reduction upon carbon dioxide enrichment decreases. An increase in the degree of volume expansion of the liquid phase brings about a dramatic initial reduction in liquid phase viscosity. Viscosity reduction appears to be linear in excess of 300% liquid phase volume expansion. (c) 2006 Elsevier B.V. All rights reserved.