DEF FAQ: Frequently Asked Questions About Diesel Exhaust Fluid

DEF Frequently Asked Questions

DEF and Diesel fuel tanks

What is DEF?

Diesel Exhaust Fluid (DEF) is a solution of synthetic urea and deionized water. It is injected into the exhaust stream of diesel powered vehicles to reduce toxic emissions. 

Why do I need DEF?

DEF is a critical component in Selective Catalytic Reduction (SCR) technology. In an SCR system, harmful nitrogen oxides (NOx), carbon monoxide, and hydrocarbons are turned into nitrogen, water, and small amounts of carbon dioxide. Due to new EPA restrictions, SCR is now used by all diesel vehicle manufacturers.

Is DEF dangerous?

No, DEF is a non-toxic and stable solution. Vehicles transporting DEF do not need to use a Department of Transportation hazard placard. DEF can however corrode some metals (like aluminum, zinc, copper, and carbon steel) so that is why it is stored in poly or stainless steel containers. Be sure to ask your DEF supplier for a current Safety Data Sheet (SDS).

Does DEF go bad?

When DEF is stored out of direct sunlight and kept between 15° F and 77° F then it will have a shelf life of about 2 years. Sunlight and temperatures outside this range will reduce its shelf life and cause it to degrade faster. DEF storage containers should contain a visible expiration date.

Can DEF freeze?

Yes it certainly can…DEF freezes at 12° F. Since storing DEF in a warm location is not always a convenient option, investing in a DEF storage heater will save you a lot of time and hassle during the winter months.

How much DEF will my SCR vehicle use?

DEF consumption rates will be 2-3% of your diesel fuel rates. That means you will need about 2-3 gallons of DEF for every 100 gallons of diesel fuel. These usage rates can vary slightly depending upon the make and model of your vehicle, so make sure to consult your vehicle’s user guide to be sure.

What Is this white, chalky residue around my DEF container?

If the deionized water evaporates out of the DEF solution, you will see solid urea crystals form (similar to when salt water evaporates). Make sure your container caps are sealed tight to prevent as much evaporation as possible. If you see white residue around the tips of your pump nozzles, simply remove it with a wash of deionized water.

What happens if my vehicle runs out of DEF?

Most diesel vehicle manufacturers have added instrumentation to prevent this problem. Depending upon the make and model of your vehicle, this can include DEF gauges, indicators, and other on-dashboard displays. If the warnings to refill the DEF tank are ignored, the vehicle will enter “limp” mode and experience a performance reduction until you refill.

Powerblanket DEF Solutions

Here at Powerblanket, we proudly offer winter heating solutions that are perfect for your DEF needs. Our specialized DEF storage heaters are equipped with thick vinyl shells and even heating that prevent freezing down to -20° F. They keep your DEF within its ideal temperature range to maintain the chemical concentrations and ingredient purity you rely on. In addition, our easy access flap enables you to still use your pump housing all winter long.

Powerblanket infographic about DEF storage heaters

Contact us today to find the perfect DEF solutions for your needs at 855-581-4564 or [email protected]

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


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.

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