DEF Freezing and DEF in Cold Weather

The Polar Vortex is sliding down over the country.  Have you taken precautions to prevent DEF freezing in the increasingly cold temperatures swiftly approaching?  We have tips and guidelines to help you with DEF in cold weather.

Understanding DEF and SCR

Diesel Exhaust Fluid (DEF) is a non-hazardous solution, which is 32.5% urea and 67.5% deionized water. DEF is sprayed into the exhaust stream of diesel vehicles to break down dangerous NOx emissions into harmless nitrogen and water. NOx is an element in exhaust that has been blamed for acid rain, smog and raising the overall greenhouse gas levels of the planet.  DEF is not a fuel additive and never comes into contact with diesel. It is stored in a separate tank, typically with a blue filler cap. This system is called Selective Catalytic Reduction (SCR).  SCR and DEF have been used for decades in other commercial and agricultural applications.

Storing DEF

DEF should be stored in a cool, dry, well-ventilated area. The ideal storage temperature for DEF is between 15ºF and 65ºF (-9ºC and 18ºC). It should not be exposed to direct sunlight for long periods of time as the urea will decompose. When possible, DEF packages and bulk storage should be kept indoors in temperature-controlled environments.  Use the right container. DEF is mildly corrosive and should be stored in containers of HDPE plastic or stainless steel. 

DEF Freezing Protection guide graphic

Need to protect your DEF from freezing? Powerblanket’s DEF storage heaters are designed specifically to maintain optimal temperatures for Diesel Exhaust Fluid. With precise temperature control and even heat distribution, you can prevent freezing and degradation of your valuable DEF supply. Our heaters are durable, plug-and-play operation, and customized sizing is available.

DEF Expires

Check the expiration. The storage life of DEF varies. The urea is vulnerable to degradation from sunlight and higher temperatures. In favorable storage conditions (proper container, away from direct sunlight, temperatures between 15 and 65°F), DEF can maintain its qualities for about 12 months. 

Be Good to DEF

Handle it like fuel. Per EPA guidelines, vehicles using DEF must include sensors to continually analyze the quality of the DEF being consumed. These sensors will trigger a fault code whenever an imbalance is detected. Most commonly, this results from a higher percentage of water as a result of foreign matter, condensation or rainwater in the DEF storage container or during transfer.  The quality and integrity of DEF must be maintained for proper machine operation. It must be protected against evaporation and temperature extremes, and kept free of contaminants. Doing so could change DEF density, impacting its performance.

At what temperature does DEF freeze?

DEF Freezing

DEF, because of the urea, doesn’t have the freezing point of water. The urea mixture has a much lower freezing point of 12°F/-11°C. This solution doesn’t break into just urea and just water, either. The solution freezes and thaws at the same rate. This means that at no point does the DEF freezing cause the solution to become over-concentrated or diluted. DEF will begin to slush and then freeze.  There is no harm to the product which means that the urea solution is still safe to use if it has been frozen.

DEF Freezing and Expansion

Though it is safe to use again once thawed, expansion from freezing could cause problems.  Since DEF is a mixture of deionized water and urea, it reacts somewhat like water in that it does expand when frozen. DEF freezing usually causes about a 7% expansion. It is important to note that DEF freezing is usually taken into account when creating the packaging and tanks that are supposed to hold DEF. DEF packaging and tanks allow for expansion. However, one must be aware of the expansion of DEF when filling.  When storing equipment overnight or longer in temperatures that could result in DEF freezing, it is important to make sure the DEF tank on the equipment is not completely full or that it has an appropriate heat source. This will allow for expansion and help prevent cracking of the storage reservoir.

How to Prevent DEF Freezing?

DEF freezing was taken into account by the OEMs prior to creating the Selective Catalytic Reduction (SCR) systems. Therefore, the SCR systems are designed to provide heating for the DEF tank and supply lines; however, if the vehicle is shut down and exposed to freezing temperatures, then it is likely that the DEF will freeze. Diesel owners do not need to worry about DEF interfering with their vehicles, however. If DEF freezes when the vehicle is shut down, startup and normal operation of the vehicle will not be inhibited. In most cases, the SCR heating system will quickly thaw the DEF in order to return it to liquid form and resume normal operation.


Can Anything Be Added to Prevent DEF Freezing?

Many want to know if anti-gelling or freeze-point-improver can be added to the DEF mixture to prevent freezing. DO NOT put additives into the urea solution because DEF must remain pure. The quality of DEF is extremely important for proper performance. Adding any additives would damage its ability to perform correctly and could even result in damage to the SCR system. No additives are approved for DEF at this time.

DEF Tote Heaters from Powerblanket

Powerblanket has a solution for DEF freeze prevention:  Powerblanket DEF Tote Heaters maintain optimal heating conditions for temperature-sensitive materials.  Powerblanket DEF Tote Heaters are temperature-specific for the Diesel Exhaust Fluid to protect from freezing and maintain optimal temperatures.

DEF FreezingHere’s How

  • Distribute heat evenly around the tote
  • Fully enclose and heat the tote and pump housing unit
  • Designed to be durable and weather-resistant
  • Easy access to fill with a removable top
  • Simple plug-and-play operation, the temperature is automatically regulated
  • Safely heat and protect a wide variety of chemicals and materials
  • 330 and 275-gallon versions feature an easy-to-access flap to the pump
  • Heated wraps for customized DEF bulk storage tanks are available upon request
  • Include a frame to easily enclose and heat pump and hose





The Powerblanket DEF tank heater is the most efficient and effective way to heat and store diesel exhaust fluid.

Protect your DEF from winter temperatures with DEF Tote Heaters

Check out our 275-Gallon DEF Tote Heaters


Shelby Thompson

Shelby Thompson is the head of standard product sales for Powerblanket. He has a distinguished military career, having served in both Afghanistan and Iraq. In his time in the Marines, Shelby acquired an impressive skillset that he now uses in his current role. When he's not working, Shelby loves spending time outdoors with his wife, son, and daughter. He is also a semi-keen hunter, fair weather fisherman, and shooter. Unfortunately, Shelby also has something of an unlucky streak when it comes to Fantasy Football at the company.

7 thoughts on “DEF Freezing and DEF in Cold Weather

  1. my def filler line is frozen and i cannot get warm def to go into tank. will it hurt to drive even without enough def being introduced to engine. my tank registers only 1/8 tank full!

  2. We have a 2013 Chevy diesel transit bus, that is still on warranty and has froze up every time it gets below 15 degrees. The Chevy dealers tell us the only thing we can do is keep it in a heated garage. We have had it to the Chevy dealers many times to get it in and resest the DEF tank. They replaced the DEF heater too, but nothing helps. I have had diesels for over 30 years without any problems. We have a 2013 Ford diesel pickup and do not have any problems. Why does GM not come out with some kind of heater or “fix” that works??????????? GM doesn’t care that we have routes that can’t go because the DEF is frozen. These people count on this transit bus in rural North Dakota to get to the doctor!

  3. I am all for protecting the environment but they need to come up with an additve for the Def system. I am an owner of Deisel trucks for my business,and we live in the north. It is very expensive when your truck freezes up at your work place it is not just the $1000.00 tow bills but know you have motel and meals for your employees. This is an expense you did not budget on ,and we shouldn’t have to.

  4. Do you make a blanket for 2016 canyon Gmc 2.8 diesel def tank. Mine freezes up and goes into limp mode. My dealer said not can be done. They are avoiding the problem when I would like to correct the problem

    1. Powerblanket can create an efficient blanket for any application. If you don’t see the size you need, our custom department will happily help you out. Please contact Shelby ([email protected]).

  5. is there amy possible way to defrost the def fluid compartment …..understanding the the filter has to be changed

Leave a Reply

Your email address will not be published. Required fields are marked *