HOT SHOT'S SECRET PREMIUM DEFender is engineered to clean and prevent Diesel Exhaust Fluid (DEF) crystal buildup. Harmful deposits in the Selective Catalytic Reduction (SCR) system can reduce performance, increase fuel use, and lead to costly repairs or downtime. Premium DEFENDER cleans the entire SCR system by dissolving crystal deposits that form in the tank, pump, heater, sender, lines, injector, decomposition tube, reactor and mixer. When the SCR system doesn't operate as intended, engine fault codes can occur and trigger a vehicle to enter "limp mode" where the vehicle will drive slowly, or become un-drivable. Premium DEFENDER restores DEF function, helps to avoid "limp mode," and with regular use maintains efficiency of the SCR. Triple-filtered for purity. Ash and dye-free formula. For use in all SCR-equipped diesel engines including cars, trucks, semis and equipment, will not void OEM warranties when used as directed. Fully compatible with all brands of DEF.