Yes, it is necessary to preheat your gas grill before cleaning it. Preheating the grill helps to loosen any food particles or grease, making it easier to clean. It also helps to sanitize the grill grates, ensuring that they are clean and ready for your next use. By preheating the grill, you are not only ensuring effective cleaning but also promoting food safety. So, it’s a good practice to preheat your gas grill before cleaning.