The data presented relates to the crystallisation of the long chain hydrocarbon eicosane (C20H42), from supersaturated toluene solutions in the absence/presence of a commercially available cold-flow improver additive (IA) at different solution treat rates (0, 0.1, 0.5, 2, 3, 5 and 10 wt% IA with respect to eicosane), over four solution concentrations. Data is collected by transmission vs. solution temperature experimental investigations and is analysed through a conventional transmission analysis route (STR) and a reanalyzed route that takes into account multiple phase transformation behaviour (RRT). Crystallisation (Tc) and dissolution (Tdiss) temperatures are displayed alongside Solubility (Te) and supersolubility (T(c,l)) data over the range of solution concentrations and cooling rates used under a polythermal crystallisation methodology for each analysis route. STR analysis data is displayed for all solution treat rates, with RRT analysis data shown for 2wt% - 10wt% IA. The table presents RRT analysis data for each treat rate first, followed by data collected through STR analysis, for the overlapping treat rates analysed by both methods.