Let me add that using regular when premium is “required” will result in less power lower mileage and, in time, a damaged engine. Since you will end up paying more anyway due to the lower mileage, why not protect your engine and get better performance and use what is required.
NOTE: when the owner’s manual says premium only or required, it means just that. When it says recommended, then it means the car will adjust for the lower octane and prevent damage to the engine, causing reduced performance and mileage as well. Most cars fit in the “recommended” class, but there are those that do “require.”