A newly developed characterization protocol was per-formed in this study on two Canadian heavy oils, Athabasca and Morgan. This protocol focused on the sequential extraction of asphaltene subfractions based on a change of polarity of a binary system, a solvent and a titrant. The selected solvent was tetrahydrofuran, and the titrant was n-hexane boiling at almost the same temperature. The resulting asphaltenes subfractions were separated by a decreasing polarity. This new protocol allowed collection of each asphaltene subfraction in addition to the determination of the asphaltene subfraction that is more responsible for high viscosity. All subfractions originating from both oils were analyzed using different analytical techniques. Trends in polarity and metal contents were observed. The high field NMR allowed detection of differences between the fractions and determination of the fractions characteristics responsible for high viscosity. The maltenes were further fractionated into saturate, aromatic, and resin fractions.