A conventional base stock, solvent refined (SR) and a hydroisomerized base stock (HI) in which differences in behavior of Pour Point Depressant Additive are observed, have been dewaxed and these oils and their fractions have been characterized by analytical methods and thermal analysis. Differential scanning calorimetry (DSC) is a rapid and valuable technique for characterization of the thermal behavior of lubricating oils, allowing the determination of crystallization temperature and amount of precipitated fractions versus temperature. Differences between these basestocks, more particularly in the amount of crystals which precipitate versus temperature can explain selective effectiveness of pour point Depressant (PPD) additives.