Royal Purple HPS 10W-40 motor oil is specifically formulated to maximize performance and meet the demands of high-performance engines and modified engines. HPS, high-performance street motor oil is recommended for vehicles no longer under manufacturer warranty and for those seeking a higher level of performance and protection. Royal Purple’s HPS is fortified with a high level of zinc/phosphorus anti-wear additive and Royal Purple’s proprietary Synerlec® additive technology. HPS outperforms other leading high-performance synthetic oils and conventional lubricants for both gasoline and diesel high-performance engines. Royal Purple HPS motor oil responds to increased pressure with increased viscosity. Thus Improved sealing between the piston ring and cylinder wall which maximizes power.