Royal Purple® – Duralec Ultra™ High Performance Diesel Motor Oil Greater wear protection Greatly extends oil drain intervals Superior corrosion protection Reduces exhaust emissions Keeps engines clean API warranty compliant Will not harm seals Related posts: Royal Purple® – Duralec Super™ High Performance Synthetic Motor Oil Royal Purple® – XPR™ Ultra Light Extreme Performance Synthetic Racing Motor Oil Royal Purple® – API-Licensed™ Multi-Grade High Performance Motor Oil Royal Purple® – HPS™ High Performance Street Synthetic Motor Oil Posted In: Replacement Engine PartsTagged In: Royal Purple