What every truck operator needs to know about Diesel Exhaust Fluid (DEF)
So what is DEF fluid?
Diesel Exhaust Fluid (DEF) is a non-hazardous, environmentally friendly solution comprised of 32.5% urea and 67.5% de-ionized water. It is used in diesel vehicles such as pickup trucks, RVs and SUVs that have the built-in Selective Catalytic Reduction (SCR) technology.
Produced to an international standard (ISO 22241), DEF was developed in order to meet the 2010 EPA Diesel Emission Standards to reduce the amount of particulate matter and nitrogen oxide (NOx) emitted into the air from on-road diesel engines.
Engine manufacturers have since deployed a variety of means to comply with the 2010 diesel emissions regulations to improve particulate matter emissions, evolving a variety of recently implemented diesel truck technologies such as SCR and Exhaust Gas Recirculation (EGR).
As of 2010, all new diesel pickup models now contain a separate tank (typically with a blue filler cap) and an SCR system, where DEF is used as a consumable to lower NOx concentration in diesel exhaust. The organic, non-toxic fluid never comes into contact with diesel (which gets stored in a separate tank) and is therefore not a fuel additive.
How exactly does DEF work?
DEF serves as a reducing agent by setting off a chemical reaction known as a "reduction". As the engine is running it converts pollutants (NOx) into nitrogen, water, and tiny amounts of carbon dioxide (CO2), which get expelled through the vehicle tailpipe.
The role of the Selective Catalytic Reduction (SCR) system is that of a catalyst in that it injects DEF into the exhaust stream of your truck diesel engine and permits NOx reduction reactions to take place in an oxidizing atmosphere.
The SCR is considered as an "after-treatment system" since it treats the vehicle's exhaust after combustion. It is called "selective" because it reduces levels of NOx using ammonia as a reductant within a catalyst system, where DEF is broken down to produce the oxidizing ammonia in the exhaust stream. To learn more about the SCR process, check out a previous post on the topic here.
Where can I buy DEF?
DEF is available through your local dealership, distributor and major truck stops. Even roadside assistance personnel will carry it. To search for a location nearest you that sells DEF, check out DiscoverDef.ca and use their search form.
Bulk DEF filling stations are also starting to sprout up at truck and diesel stations across North America. Call 1-877-245-5518 for your nearest location.
How many kilometers will a full tank of DEF last?
A full tank of DEF should last you about 8,000 kilometers.
What are the maintenance implications for DEF?
DEF system maintenance is simple and easy to do (ex: the DEF filter should only take a few minutes to replace), and it can be done concurrently with your current routine of normal maintenance.
Does temperature affect DEF?
At -11 degrees Celsius, a 32.5% solution of DEF will begin to crystallize and freeze, but thanks to the DEF tank thawing process, freezing and thawing have no effect on the performance of DEF along with the SCR system being designed to provide heating for the DEF tank and supply lines.
However just as water expands when it freezes, as 67.5% de-ionized water DEF is prone to expansion as well, with about 7% growth in volume when frozen. So while DEF packaging and tanks were designed to allow for expansion, it's still important to be expansion conscious by NOT filling your DEF tank up completely during cold weather (since it can expand and potentially cause the container to crack).
What are the storage requirements for DEF?
Keep your DEF fluid out of direct sunlight and store it in a cool and dry place. The ideal storage temperature is up to 25 degrees celcius. Also bear in mind that DEF will degrade over time, with temperature and exposure to sunlight weighing heavily on its shelf life which can range from 1-2 years in ideal storage circumstances.
What happens if you run low on DEF?
Running out of DEF is almost as bad as running out of diesel fuel. Since visual indicators in the cabin provide low-level warnings, you will be notified before you run completely out, so pay attention! But if you're already in the low zone, the next time you start your vehicle you'll notice a significant reduction in power, which is why it's smart to have a bottle of DEF and funnel on hand at all times. You most definitely don't want to let your DEF run out and cause a bottleneck on the road!
