RISLONE® DEF CRYSTAL CLEANTM Diesel DEF & SCR Emissions System Cleaner is a propriety blend of DEF (Diesel Exhaust Fluid) / AdBlue® compatible cleaning agents and surfactant detergents specifically designed to be safe to use and work on SCR (Selective Catalyst Reduction) systems. DEF Crystal Clean gives a cleaning effect on the entire SCR system by working to dissolve the white crystal deposits that form in the tank, pump, heater, sender, lines, injector, decomposition tube / reactor and mixer. These deposits can interfere with the normal operation of the SCR emissions system and engine, increasing fuel consumption and reducing engine power. This reduced power can lead to operating in limp mode where the vehicle will drive slowly, or become undrivable. This process restores function and with regular use maintains efficiency of the SCR. DO NOT ADD TO DIESEL FUEL TANK. INSTRUCTIONS: DEF Crystal Clean is specifically designed to only be installed in the Diesel Exhaust Fluid / AdBlue tank which usually has a blue cap. Do not add to the diesel fuel tank. * Light Truck or Mid-Size to Large SUV - 5 to 9 gallon tank capacity install full bottle into DEF tank. *Car or Small SUV - 3 to 5 gallon tank capacity use approximately 1/2 bottle. *Medium and Heavy Duty Diesel Trucks - 10 to 20 gallon tank capacity use 2 bottles. Pour DEF Crystal Clean into mostly full DEF tank or add and fill tank with diesel exhaust fluid. If light is still on after 250 miles or a few days of driving, second application may be required, or mechanical attention is needed. NOTE: Works with all approved diesel exhaust fluids. Some vehicles use a special filling adapter to install DEF / AdBlue into the tank. For those vehicles use special funnel or pour into mostly empty DEF / AdBlue bottle and install in system.