RISLONE® DEF CRYSTAL CLEAN™ 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.