Royal Purple Motor Oil delivers superior protection and improves performance in four-cycle gasoline and diesel engines. It increases horsepower and torque, saves fuels and reduces heat, wear and emissions. It has unsurpassed oxidation stability that allows for extended oil drains and fewer oil changes, which saves you time and money and reduces the impact on the environment. Royal Purple’s motor oils are API certified. For those seeking enhanced performance in high performance vehicles not under warranty, we recommend our XPR – Extreme Performance and Racing motor oil. Royal Purple’s performance advantages come from a blend of synthetic oils plus Royal Purple’s proprietary Synerlec technology. Royal Purple Motor Oil is compatible with other mineral and synthetic motor oils. It’s available in 5W20, 5W30, 5W40, 10W30, 10W40, 15W40, 20W50, SAE 30, SAE 40 and SAE 50 weights. Why Use Royal Purple? Independent university and industry tests document the performance gains of using Royal Purple. When compared to leading synthetic and conventional motor oils, Royal Purple motor oil typically: Increases horsepower and torque by as much as 3% Reduces engine wear by as much as 80% Improves fuel economy by as much as 5% Reduces engine heat by as much as 10% Reduces emissions by up to 20% or more Performance gains vary depending on the type of vehicle, its condition, and the way it's driven.