Phase partitioning experiments conducted at Alberta Research Council (ARC) have shown that Athabasca UTF bitumen and propane mixture partitions into a solvent-rich light oil phase and a heavy-ends-rich oil phase. The partitioning may have beneficial impact on the performance of a gravity based process such as VAPEX and other solvent based processes if the low-viscosity phases carries the bulk of the oil production, and the heavy phase left in the reservoir is mostly asphaltene and essentially immobile. It is considered essential to treat the bitumen as a multi-component fluid with asphaltene as one of the components in order to determine the fluid properties of the upgraded oil in the propane based recovery process. Bitumen was treated both as a single component and as a multi-component fluid in the numerical simulations of the propane based recovery process. Fluid properties such as gas-liquid K values for components representing the bitumen (saturates, aromatics, polars and asphaltenes), as determined through CMG-WinProp earlier, was used in the numerical simulations with CMG-STARS. The challenges involved in representing bitumen as a multi-component fluid in the simulation of the recovery process is discussed.