A process for liquid-liquid extraction of an oil-blend of non-uniform oligomeric and polymeric components comprising: (a) preselecting a desired molecular weight (Mw) boundary between heavy and light components; (b) selecting an extractive solvent or an extractive mixture of solvents, which form essentially a single phase with the light components; (c) mixing the oil-blend and the extractive solvent or extractive mixture of solvents selected in step (b) at elevated temperature, which is at least at or above said fractionation temperature, and wherein the extractive solvent/mixture of solvents to oil-blend ratio is from 1:2 to 100:1; (d) allowing a phase split to form between the heavy components fraction and the light components/extractive solvent fraction at the fractionation temperature or at most 10° C. below the fractionation temperature; (e) followed by separation of said fractions.