To address the demand for less energy-intensive and greener bitumen recovery techniques, the use of multicomponent diluents through the expanding solvent steam-assisted gravity drainage (ES-SAGD) technique has garnered significant interest in recent years. In these methods, a mixture of saturated steam and a multicomponent solvent is co-injected into bitumen and heavy oil resevoirs. To better understand the complex systems of multicomponent solvent/methane/bitumen and to improve the optimization of solvent-aided thermal recovery methods, it is essential to measure and thermodynamically model the thermophysical properties of vapor-liquid equilibrium (VLE). This work presents experimental and modeling studies on the VLE of bitumen/methane/multicomponent solvent. First, experimental measurements and thermodynamic modeling of thermophysical properties of C1/bitumen, CO2/bitumen, C1/CO2/bitumen, C1/diluent/bitumen, and C1/CO2/diluent/bitumen systems are performed over a wide range of pressures (1-5 MPa) and temperatures (353.8-503.60 K) for Two solvent concentration, 30 and 50 mol%. Second, a stepwise parametrization approach is utilized to correlate the experimental data of thermophysical properties of the mixture of live bitumen and a synthesized diluent comprised of n-C4, n-C5, n-C6, n-C8, and n-C10. The experiments are carried out at a pressure range of 1-6 MPa and a temperature range of 343.15-503.15 K. Third, the effect of solvent concentration on the saturation pressure of the mixture is investigated. A set of experiments over the pressure range of 1-4 MPa and a temperature range of 313.41-459.10 K are performed. The measured density and viscosity data are modeled using the Peng-Robinson Equation of State (PR-EoS) and the modified Pederson model, respectively. Finally, compositional analysis of the vapor-liquid equilibrium (VLE) of the mixture of methane and a synthetic diluent comprised of n-C5, n-C6, n-C7, cyclo-hexane, and toluene is studied for temperatures up to 459.36 K. The measurements include the saturation pressure of the mixture, density of the saturated liquid and K-values of different components for pressures below the saturation pressure.