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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: non-toxic, non-polluting, non-flammable, non-hazardous, stable, and colorless. The downside is that it is corrosive to most metals and coatings. Anyone who has accidentally spilled DEF on their truck will tell you that is true, so be extra attentive when adding DEF to your vehicle.

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

Can Diesel Exhaust Fluid freeze?

During vehicle operation, SCR systems provide heat to the DEF tank and lines. The system thaws DEF rapidly and keeps it flowing to the after-treatment system, regardless of the outside temperature.

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

Diesel Exhaust Fluid (DEF) is formulated with 32.5% urea and 67.5% de-ionized water. In storage, or when the engine is not in use, DEF will freeze at 12°F (-11°C). At this concentration level, the area and the water freeze and thaw at the same rate – ensuring 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.


Benefits of Diesel Exhaust Fluid

If your business uses diesel-powered vehicles, you probably already know the benefits. Diesel-powered engines offer less stalling, more durability, more torque, and less fuel for mileage and refueling.

However, diesel also has disadvantages. One of the main problems with this type of engine is the increased production of nitrogen oxide or NOx. NOx is a pollutant and its formation pollutes the environment. In addition, there are government regulations to reduce NOx emissions from commercial diesel engineers.

This is where Diesel Exhaust Fluid (DEF) comes into play. This product is a supplement that is placed in the petrol tank of diesel-powered vehicles and breaks down NOx and other pollutants before these hazards are converted to DEF by the vehicle.



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. If you have any questions, give us a call and we will gladly help you out!

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