Poly(pentaerythritol adipate), poly(pentaerythritol sebacate), and poly(pentaerythritol hexadecandioate) derivatives containing different length alkyl branches were synthesized by two subsequent steps; the reaction of pentaerythritol with (C8-C16) linear aliphatic monocarboxylic acids and then, polymerization of products with (C6-C16) linear aliphatic dicarboxylic acids, using 1% para toluene sulfonic acid as a catalyst. The products were purified and characterized by FTIR, 1H NMR, and 13C NMR spectroscopy. End group analysis was also used as a molecular weight determination technique. The drag-reducing properties of those polymers were investigated in the turbulent flow of Basrah light crude oil using a closed-loop circulation system. Some were found to perform very well DRA and drag reduction efficacy of polymer was further found to be dependent on flowrate, polymer concentration, medium-temperature, and its chemical structure. Also, the effect of the imposed mechanical shear on the polymer stability as a function of time has been investigated using a cylindrical rotator device. It was observed that distance between branch points plays a direct role in contributing to the polymer performance and its mechanical stability.