Doctorx Injector FSM-4- Fuel System Maintenance Cleaner and Fuel Injector Cleaner - (4-pack - 11oz Bottles) FSM's detergents clean intake valves, and is designed to help prevent coking of the injector pintle and seat caused by varnish. FSM contains the most powerful high temperature detergents designed to clean fuel injectors. Add one bottle on a fuel tank Fill-up. Recommended to be added when you do an oil change and this is all it takes to help keep your injectors clean and flowing freely. The only Silver Bullet you can have to keep your car from unloading your wallet is Maintenance.