DEF (Diesel Exhaust Fluid) is carefully regulated by the American Petroleum Institute and, on average, is a mixture of 2/3 deionized water and 1/3 synthetically made urea. The DEF is stored in a separate, insulated, heated tank and typically has a blue filler cap.

Before 2008, owners of 3/4 and one-ton pickup trucks enjoyed the fact that there was no smog equipment on their trucks; however, in 2008 the EPA required diesel particulate filters on these trucks. Truck owners also had to get biannual smog tests that included a thorough visual inspection to make sure all the parts were still on the truck. In 2010 the regulations got tighter. Manufacturers had to figured out how to cut down the bad nitrogen oxide levels and still make more power and torque – one of the solutions was the use of selective catalytic reduction.

In selective catalytic reduction, diesel exhaust fluid (a mixture of urea and deionized water) is sprayed into the exhaust stream to break down the generated NOx into harmless nitrogen and water. Because the fluid is introduced in the exhaust (often called after-treatment technology) it provides manufacturers the ability to build as much power as they want and abide by EPA regulations cutting back on NOx emissions.

How does the use of DEF affect you?

Cons: Trucks with DEF cost a bit more, DEF requires some room in your truck, and DEF adds a nominal amount of weight to your truck.
Pros: Optimized combustion, better fuel efficiency, increased power, reduced maintenance, fewer regenerations, less wear on the engine, plus it yields harmless nitrogen and water into the atmosphere, and it’s highly reliable.

Some facts about DEF:

The rate of DEF use between fill-ups is about 2.5 gallons for approximately 800 miles of travel depending on how much the person is hauling. It takes about 2-years at a constant 120 degrees for DEF to turn into ammonia and evaporate.

There are different read-out gauges, depending on what year and model truck is being operated, that the EPA requires all truckmakers to install as a warning system to let drivers know the status of their system. For example, in a RAM there is a fuel-gauge-like readout; a GM will have a a digital indicator and a Ford with have a simple “low” light indicator.

DEF fluid can be purchased at several locations including: Walmart, TravelCenters of America, Flying J Truck Stops, Love’s Travel Stops, Petro Stopping Centers, and Pilot Travel Centers, to name a few. Plus, it can be purchased by the gallon at many auto parts stores like O’Reilly’s and Advance Auto.

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