Solubility of carbon dioxide in n-octadecane and in three binary mixtures of n-octadecane and n-decane (0.25, 0.5, and 0.75 mol fractions of n-decane) has been measured at 323 K and at the pressures (1 to 6) MPa. Prior to phase equilibrium measurements, the density and viscosity of n-octadecane and of prepared binary mixtures were measured. Then, the phase behavior measurements were undertaken with an in-house designed PVT apparatus. The solubility of carbon dioxide in liquid hydrocarbons and its effect on the physical properties were examined. Increase in the pressure caused an increase in the carbon dioxide solubility and consequently, a decline in the viscosity of saturated liquid phase and an increase in the density of gas-expanded liquid were observed. The carbon dioxide solubility was lower in the heavier liquid mixture. The experimental data were well modeled with Soave-Redlich-Kwong and Peng-Robinson equations of state. Both equations of state have almost the same predictions for solubility while the Peng-Robinson equation of state is superior for density prediction.