NüDef Diesel Exhaust Fluid Treatment, Additive & Stabilizer

A DEF fluid additive helps prevent crystallization, lowers the freezing point and protects the SCR system from scaling and deposits. It treats the diesel exhaust fluid, not the fuel.

Add NüDef with each DEF fill-up, or according to your maintenance schedule, for consistent protection.

One bottle treats up to 25 gallons of DEF. Each dose treats 2.5 gallons, so a bottle holds ten doses.

Regular use of a DEF stabilizer helps prevent the common failures caused by crystallization, scaling and deposit formation in the SCR system. It does not replace a part that has already failed.

NüDef works with all diesel vehicles that use DEF, including cars, trucks, SUVs, RVs, commercial trucks, marine engines, generators and heavy machinery.

Yes. NüDef lowers the freezing point of DEF, which adds protection in cold weather when DEF is most vulnerable and keeps fluid moving while the tank heater does its work.

Store it in a cool, well-ventilated place away from heat sources. Keep the container tightly closed and protect it from sunlight.

Yes. Request the Safety Data Sheet through the contact page and we will send it.

A DEF additive. There is a real difference and it matters. A diesel fuel additive goes in the fuel tank and treats the fuel itself. NüDef is a diesel exhaust fluid additive: it goes in the DEF tank and treats the fluid your SCR system injects into the exhaust. Never put a fuel additive in the DEF tank or DEF in the fuel tank. If you are searching for a diesel fuel additive for DEF systems, this is the product that treats the DEF side.

Fresh certified DEF is the right starting point, and nothing replaces it. What fresh fluid cannot do is stay fresh: heat, cold and storage time push urea out of spec, and crystals form on sensors, floats and dosing valves as it drifts. NüDef keeps the urea in solution through those swings, so the fluid the truck reads next month is still the fluid you poured. One 8 oz bottle treats up to 25 gallons of DEF.

Any engine with an SCR system that uses DEF: pickups, semis, agricultural and construction equipment, and stationary machines. If it has a blue cap, it qualifies. Trucks without a DEF tank (pre-2010 on-road diesels and deleted trucks) have nothing for the product to treat.

Yes. NüDef is compatible with all brands of certified urea DEF and AdBlue, from pump DEF to boxed jugs and bulk delivery. Some premium DEF products advertise their own additive package; NüDef is a stabilizer added to the fluid you already use, so follow that maker's guidance if you combine them. The brand-by-brand picture is in our DEF brand comparison.

Look at the places crystals show up first. The fill neck, the cap and the header assembly stay free of white crust, partially used jugs stay clear instead of clouding or forming a skin, and the truck stops throwing quality and pressure warnings between fills. If deposits were already present, expect them to loosen over several treated fills rather than overnight.

It is formulated to help dissolve crystallized DEF deposits, and light buildup in lines and on the injector typically loosens with regular treated fills. A fully blocked injector, a seized pump or a crusted level sender needs service first; treat the fresh fill afterward so the new part does not fail the same way. If the truck is already in derate, read what happens when DEF runs out for the countdown rules.