If you’ve been in the market for a new tractor, most likely you’ve heard of, or are already using, diesel exhaust fluid, or DEF. It’s a clear, nontoxic fluid marketed under such names as AdBlue, AirOne and AGCO DEF. Tractor makers are using it as part of selective catalytic reduction, or SCR, technology to meet the Final Tier 4 emissions cuts, which go into effect Jan. 1.

DEF is a blend of water and urea that is nontoxic and nonflammable. It is injected into the exhaust stream and neutralizes engine pollutants. While DEF is relatively easy to use, storing it and maintaining purity requires some attention, especially in winter. Here are some basic instructions:

  1. Know that it will freeze. DEF is a water-based solution, so just like water, it will freeze, says Keith Kladder, marketing manager at AGCO Parts North America. Take precautions when using DEF in extreme winter conditions. “DEF will begin to ‘slush’ before it freezes and will ultimately freeze into a solid state when the fluid temperature reaches 12 degrees F,” Kladder says. “However, the process of freezing DEF has no effects on its quality or performance.”
  2. Leave room for expansion. “DEF expands upon freezing by upward of 7%,” Kladder continues. “Thus, 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. This will allow for expansion and help prevent cracking of the storage reservoir.” During winter, once the tractor is started, the DEF will thaw quickly and return to its usable state, he says.
  3. Store indoors. DEF packages and bulk storage should be kept indoors in temperature-controlled environments.
  4. Use the right container. DEF is mildly corrosive, and should be stored in containers of HDPE plastic or stainless steel, says Doug Page, Case IH parts marketing manager for fluids. Other metals may corrode when in contact with DEF and cause contamination,
  5. Change the filter. “The injectors that meter DEF into the exhaust stream are precision instruments with tight tolerances, similar to fuel injectors,” says Page. “Case IH SCR systems have a cartridge filter inside the pumping module to protect these injectors, with a recommended 1,200-hr. service interval.”
  6. Check the expiration. The storage life of DEF varies, Page says. Its urea is vulnerable to degradation from sunlight and higher temperatures. In favorable storage conditions (proper container, away from direct sunlight, temperatures between 12 and 86 degrees F), DEF can maintain its qualities for about 12 months.
  7. Handle it like fuel. Per EPA guidelines, vehicles using DEF must include sensors to analyze continually 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.

Page says 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.

“The simplest way to think about DEF might be to handle it as you would diesel fuel in terms of keeping it totally free of any contaminants and moisture, and storing it in a proper container kept in a cool, shaded place,” he concludes.

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