Your plugs should be changed at about 100,000 miles. However, are you experiencing a specific performance problem? Don't just automatically replace your plugs hoping that it will correct a problem. Usually modern vehicles run the same after a "tune-up" as before the tune-up. If you don't like the way it is running, starting, or accelerating, you may have a specific problem that needs to be diagnosed and corrected. But, if it runs great and you just want to keep it running great, 100,000 miles is a great time to change your spark plugs!!