Many people believe that using a higher Grade/Octane than called for in your User Manual is better for your engine. It is not. Using a higher octane than specified for your engine is not better for the engine and can cause damage. Too high Octane can cause Un-burned fuel to pass through the combustion chamber into your exhaust system damaging it including your catalytic converter. An exception is at high elevation. There lower octane fuel than specified for normal driving elevations is recommended . If you go to a gas station in high elevation locations like in Colorado you will notice that the octane rating for each grade (Reg./Mid/Premium) fuel is lower than the octane ratings at lower elevation location.