A thermoplastic elastomer formed by a process comprising the steps of dynamically vulcanizing a rubber within a mixture that includes the rubber, from about 10 to about 80 percent by weight of a thermoplastic resin based upon the total weight of the rubber and the thermoplastic combined, and from about 1 to about 25 percent by weight of a polymeric processing additive based upon the total weight of the rubber and the thermoplastic combined, where the polymeric processing additive is a linear polyolefin resin that has an melt flow rate that is greater than about 1,000 dg/min, a diene-modified polyolefin polymer that has an melt flow rate that is greater than about 1,000 dg/min, from about 0.005 to about 2.00 mole percent polymeric units deriving from dienes, and a viscosity average branching index that is from about 0.4 to about 0.95, or a mixture of the linear polyolefin resin and the diene-modified polyolefin polymer, where the step of dynamically vulcanizing the rubber results in vulcanized rubber having a crosslink density of about 40 to about 180 mole per milliliter of rubber.