STP DIESEL FUEL TREATMENT 236 ml: Save fuel by keeping injectors clean. Maintain performance by preventing deposit build-up, corrosion and rust. Fight fuel line freeze and wax gel formation. Fight injector and pump wear by improving the lubricity of diesel fuel. Specifically formulated for diesel engines. STP SUPER CONCENTRATED FUEL INJECTOR CLEANER 155 ml: STP Super Concentrated Fuel Injector Cleaner contains concentrated detergents that help dissolve and remove harmful carbon, gum, and varnish deposits on fuel injectors. Without cleaning, deposits can lead to hard starts, lost acceleration and rough idling. This product is made with jet fuel, a high-quality carrier of active ingredients.