VALVOLINE PROFESSIONAL SERIES FUEL RAIL CLEANER is designed for professional use only. Detergents and cleaner added to the fuel tank may require up to three or four hundred miles of driving to remove troublesome deposits. VALVOLINE PROFESSIONAL SERIES FUEL RAIL CLEANER allows professionals to remove deposits quickly and then diagnose any mechanical failures if fuel related problems persist after cleaning. VALVOLINE PROFESSIONAL SERIES FUEL RAIL CLEANER contains powerful synthetic cleaners to clean fuel injectors immediately and removes deposits from intake valves and combustion chambers. These powerful synthetic cleaners are injected directly into the fuel system without being diluted with gasoline like cleaners added to the fuel tank. 6 Per Case.