The level of in situ upgrading of heavy Wolf Lake oil achieved by a downhole catalytic process, which is a catalytic variant of the THAI process-"Toe-to-Heel Air Injection"-has been investigated using various analytical methods. These included gas chromatography (GC), elemental analysis, simulated distillation (SIMDIS), micro-activity test (MAT), plus density and viscosity. The tests were performed on, the oil-produced from the downhole catalytic upgrading process, which was conducted in semi-scaled 3D combustion cells. The tests employed a standard hydrogen de-sulphurisation (HDS) catalyst, which was "gravel packed" around the horizontal producer well, forming an annular radial inflow type reactor. Although the analytical measurements made were necessarily selective in their scope, they nevertheless provide a good indication of what the potential may be for downhole upgrading in the field. Downhole catalytic upgrading produces a "light oil," characterized by a low viscosity of around 60 mPa(.)s, or less. The produced oil is readily converted into gasoline and diesel fractions, with a higher conversion on an FCC basis than that obtained with normal virgin bitumen vacuum gas oil. Environmentally, there are also very significant potential benefits regarding in situ removal (and retention) of heavy metals, and reduction of sulphur in the oil.