A series of highly branched polyethylene (BPE) were prepared and evaluated in a Group I base oil as potential viscosity and friction modifiers. The performance of these BPEs supports the expected dual functionality. Changes in polarity, topology, and molecular weight of the BPEs showed significant effects on the lubricants' performance with respect to viscosity index and friction reduction. This study provides scientific insights into polymer design for future lubricant development activities. (C) 2016 Elsevier B.V. All rights reserved.