STP Super Concentrated Fuel Injector Cleaner - 5.25 FL OZ STP Super Concentrated Fuel Injector Cleaner helps unclog dirty fuel injectors to restore performance to your vehicle. Safe for gasoline engines this STP fuel additive uses concentrated detergents to dissolve and remove carbon gum and varnish deposits from the fuel injector that can cause problems such as hard starts lost acceleration and rough idling. Use this car care product with every oil change or every 4 000 miles. It s compatible with cap-less gas systems and can help restore lost power and save gas.