Tips on DEF usage

January 18, 2017 5:46 pm

What is DEF?

Diesel Exhaust Fluid was created by Equipment manufacturers to meet Tier 4 final emission standards. Injecting DEF into the diesel engine exhaust system helps emission reduction by breaking down particulate matter and nitrogen oxide. DEF is 32.5% synthetic urea and 67.5% de-ionized water. DEF is: Nontoxic, Nonpolluting, Nonflammable, Nonhazardous, Stable, and Colorless but the downside is that it is corrosive to most metals and coatings. Anyone who has accidently spilled DEF on their truck will tell you that is true, so be extra attentive when adding DEF do your vehicle.  

DEF is susceptible to evaporation so be sure to tightly close lids to protect against contamination and evaporation.


Can DEF freeze? What if it is left in my vehicles over the winter?

During vehicle operation, SCR systems provide heat to the DEF tank and lines. The system thaws DEF rapidly and keeps it flowing to the aftertreatment system regardless of the outside temperature. Diesel Exhaust Fluid is formulated with 32.5 percent urea and 67.5 percent deionized water. In storage or when the engine is not in use, DEF will freeze at 12°F (-11°C). At this concentration level, the urea and the water freeze and thaw at the same rate – ensuring that you always have the correct amount of each. Engines with SCR are specifically programmed for optimal performance at this ratio.  

Like any water-based fluid, DEF expands when it is frozen.

*TIP: In cold weather, when the operator shuts the vehicle down, waiting 60 seconds before turning off the battery will allow the fluid to drain back out of the hoses and into the DEF tank.


As always, consult your OEM user manual for specific guidelines on DEF usage requirements and if you have any questions give us a call and we will help you out!

Sources: Case International, Successful Farming.