Oven cleaner can be used to remove built-up residue on a grill. First, remove the ash pan and wipe it clean. Then spray the grill grates with oven cleaner, and let the grill stand for 20 to 30 minutes. Afterward, wipe down the grates with clean paper towels.
If not used properly, oven cleaner can cause damage to a grill as it is sometimes caustic. Because it could be caustic, use gloves and closely follow the manufacturer's instructions. Manufacturers recommend deep cleaning grills twice yearly if the grill is used year-round. Oven cleaner even removes old built-up residue from gas grills.