High Performance Street (HPS) motor oil features Royal Purple’s proprietary Synerlec additive technology and is specifically formulated to meet the demands of high performance and modified engines. HPS is recommended for vehicles no longer under manufacturer warranty (for vehicles under warranty its API-licensed oils are recommended). HPS Series of motor oil responds to increased pressure with increased viscosity, providing exceptionally high film strength for reductions in engine wear and reduced engine heat. The additives found in HPS provide oxidation stability that extends oil life, uses synthetic solvency to reduce engine deposits and keeps engines clean. Royal Purple Inc.: (888) 382-6300, Online Information.