Busy cooks may want to save time by running their barbecue grill grates through the dishwasher. This is a bad idea for several reasons. A better option is cleaning grill grates properly with a wire brush, which requires little hands-on time.
Regular cooking coats grill grates with a seasoning, just like a cast iron skillet. This means you'll taste grilled meat flavor and not, as with unseasoned racks, a metal taint. Putting grill grates through your dishwasher destroys this seasoning, and it also creates a mess in the dishwasher.
Use a mild dish soap when washing grill grates by hand. In a Washington Post article, a Weber grill vice president advises using an "Earth-friendly" cleaner to avoid using harsh chemicals on your grill.
Allow your grill's heat to help you clean the grates. Turn on the grill and allow it to burn for 10 minutes; this removes food residue from the grates. Then scrape the surface with a wire brush until the grates are clean. Wash the grates once a year by hand, using warm water and mild dish soap.