The saturates and aromatic constituents of the resulting light crude oil during catalytic and thermal upgrading of Omani heavy crude oil were further characterized to elucidate the crucial role of Ni–Co/γ-Al2O3 catalyst and gas media. GC-MS analysis confirms that water-gas shift reaction (WGSR) promotes a type of hydrogenation reaction resulting in higher saturates contents of the upgraded oil in nitrogen media. In a bid to buttress the relevance of the catalyst, C7–C30 homologous series results show that the quantities of marketable components in the crude oil were higher with catalytic upgrading than thermal cracking.