Accurate predictions of heavy-oil and bitumen viscosity as a function oftemperature, pressure, and composition are required for the design of thermaland solvent-based recovery methods. In this case study, the applicability ofthe recently developed Expanded Fluid (EF) viscosity model is tested onmeasured viscosities of diluted dead and live heavy oil and bitumen attemperatures from 20 to 175°C and pressures up to 10 MPa. Density and viscositydata were collected for a condensate solvent, dead (gas-free) bitumen, and deadheavy oil from western Canada, and for the corresponding live oils and dilutedmixtures of the dead and live oils with condensate solvent. Solubility,density, and viscosity data for heavy oil saturated with carbon dioxide(CO2) were obtained from the literature. The model was fitted to thedata of the dead oils and the condensate with average relative deviations lessthan 11%. The viscosity of the live bitumen and heavy oil was then predicted towithin 21 and 31% of the measured value on the basis of measured and calculatedlive-oil densities, respectively. Diluting the live and dead bitumen with 3 to30 wt% condensate or carbon dioxide reduced the viscosity by one to threeorders of magnitude, and the viscosities were predicted with an averagerelative deviation less than 16 and 24% on the basis of measured and calculatedmixture densities, respectively.