Frequently Asked Questions
What is Diesel Exhaust Fluid (DEF)?
Why are manufacturers using Selective Catalytic Reduction (SCR) to meet the 2010 guidelines?
What fuel saving can I expect from a truck equipped with Selective Catalytic Reduction (SCR) technology?
How much Diesel Exhaust Fluid (DEF) will my truck consume?
What is the difference between agricultural urea and the urea used in Diesel Exhaust Fluid (DEF)?
What will happen if my truck runs out of Diesel Exhaust Fluid (DEF)?
What is the shelf life of Diesel Exhaust Fluid (DEF)?
Is Diesel Exhaust Fluid (DEF) corrosive?
Do I need to wear protective clothing when filling up the DEF tank?
What should I do if a spill DEF?
How does Selective Catalytic Reduction (SCR) affect a vehicle's performance?
Where can I buy Diesel Exhaust Fluid (DEF)?
Is there any danger of filling the Diesel Exhaust Fluid (DEF) tank with diesel and what problems will it cause?
A large part of Diesel Exhaust Fluid (DEF) is de-ionized water do I have to worry about the tank or other parts of the Selective Catalytic Reduction (SCR) system freezing?
Are there any heavy-duty truck manufacturers that don't use Selective Catalytic Reduction (SCR) technology to meet 2010 regulations?
When was Selective Catalytic Reduction (SCR) technology first used?
How much can I expect to pay for Diesel Exhaust Fluid (DEF)?
What is Diesel Exhaust Fluid (DEF)?
DEF is a non-toxic solution of 32.5% urea in de-ionized water. This fluid is sprayed into the exhaust stream of diesel vehicles to cause a chemical reaction and break down dangerous NOx emissions into harmless nitrogen and water. This system is called Selective Catalytic Reduction (SCR) and can be found on almost all 2010 model year heavy duty trucks and many diesel pickups and SUVs.
DEF is not a fuel additive and never comes into contact with diesel. It is stored in a separate tank, typically with a blue filler cap.
Why are manufacturers using Selective Catalytic Reduction (SCR) to meet the 2010 guidelines?
The Environmental Protection Agency's latest emissions rules for diesel vehicles of all sizes are some of the most stringent emission standards in the world. The majority of light and heavy-duty diesel vehicle manufacturers came to the conclusion that the only way to meet these rules without compromising engine performance and fuel efficiency is SCR.
What fuel saving can I expect from a truck equipped with Selective Catalytic Reduction (SCR) technology?
Because SCR is an emissions control technology installed in the exhaust, manufacturers are able to tune engines to boost performance and achieve large fuel savings in their 2010 model trucks. The extent of these savings will vary, but fleet experience with heavy 2010 heavy duty trucks suggests fuel savings of around 5% compared to 2007 models with similar engine specifications. PACCAR, Daimler and Cummins all use this figure in their 2010 model specs. Reports from customers using off-road machines with SCR are reporting fuel savings of 5% and higher.
You can read more about the specification for individual manufacturers at our Your Truck page.
How much Diesel Exhaust Fluid (DEF) will my truck consume?
Diesel Exhaust Fluid (DEF) consumption is measured as a ratio of diesel fuel, sometimes called the "dosing rate". A good starting point for this ratio is 3% and this figure has been widely used by heavy-duty truck manufacturers. This means that if your truck has a fuel efficiency of six miles per gallon it will use 1.5 gallons of DEF every 300 miles.
Feedback from a number of fleets, including Penske Truck Leasing, suggests that the dosing rate is slightly lower than originally predicted by manufacturers, at around 2%. You can calculate your truck or fleet DEF usage on discoverDEF.com's Fleet Supply page.
What is the difference between agricultural urea and the urea used in Diesel Exhaust Fluid (DEF)?
DEF uses automotive grade urea which has a much higher purity than its agricultural counterpart. Using a lower-quality urea will cause degradation of the Selective Catalytic Reduction (SCR) system, eventually causing the truck to break down. In the short-term it may also cause the sensors to believe the truck's DEF tank is empty and prompt a derating event, which reduces engine power and eventually prevents the engine from restarting.
What will happen if my truck runs out of Diesel Exhaust Fluid (DEF)?
The EPA requires vehicle manufacturers to put measures in place to ensure that vehicles cannot run without DEF. Most manufacturers have approached this in a similar way. Before a truck's DEF tank runs empty the driver is given a series of alerts on their dashboard displays (much the same way as if they were running low on diesel). Generally speaking, when the DEF tank level drops below 10% an amber warning lamp will come on, at 5% this lamp starts flashing and below 2.5% a solid amber warning light is displayed.
If the truck is allowed to run out of DEF completely, the engine's power is reduced. This generally follows the next intentional key-off, when vehicle speed will be limited to 5 mph and a solid red warning will be displayed.
What is the shelf life of Diesel Exhaust Fluid (DEF)?
DEF has a shelf life of two years. However, this can be reduced if the fluid is exposed to direct sunlight for a long time or if the temperature of the DEF remains above 77°F (25°C) for sustained periods. All DEF packaging should be labeled with the expiry date.
Is Diesel Exhaust Fluid (DEF) corrosive?
DEF is not toxic, harmful or dangerous. In fact, of all the fluids used in a truck like diesel, engine oil, brake fluid, antifreeze and windscreen wash, DEF is the least hazardous. However, DEF is corrosive for some metals such as carbon steel, aluminium, copper and zinc. Your DEF supplier can advise you further. ISO 22241 provides a list of materials that are recommended and not recommended, but makes it clear that neither list is exhaustive.
Do I need to wear protective clothing when filling up the DEF tank?
No. If you do spill any DEF on your clothing, simply rinse it off with water or wipe it away.
What should I do if a spill DEF?
If you spill a small amount of DEF, it can be washed away with water or wiped up. If you leave it to dry it will turn into white crystals. These can be washed away with water. If you spill a large amount of DEF then contact your DEF supplier for advice. Remember that urea is widely used as a fertilizer so small amounts of DEF can be disposed of by diluting with water and spraying on your lawn or garden.
If I switch Diesel Exhaust Fluid (DEF) suppliers, what should I do with the fluid which remains in bulk storage tanks and do I need to have them cleaned out?
No, simply run the tank as empty as possible before refilling. DEF is a pure chemical, so your bulk storage tank never needs to be cleaned out unless it is contaminated by a another substance.
How does Selective Catalytic Reduction (SCR) affect a vehicle's performance?
Since the introduction of environmental legislation truck manufacturers have battled to reduce emissions while maintaining and improving engine torque. Selective Catalytic Reduction (SCR) is an aftertreatment technology, meaning it deals with emissions without using in-engine controls like Exhaust Gas Recirculation (EGR), this has allowed manufacturers to tune engines, improving fuel efficiency and increasing torque.
Where can I buy Diesel Exhaust Fluid (DEF)?
discoverDEF.com has extensive listings of truck stops and retail locations for DEF in jugs or by pump, and suppliers that can deliver to your homebase on our Fleet Supply page. You can use the Search page to find a supplier near you.
Is there any danger of filling the Diesel Exhaust Fluid (DEF) tank with diesel and what problems will it cause?
The filler necks of DEF tanks are smaller than the nozzle used to dispense diesel, making it difficult to fill the DEF tank with diesel fuel. The DEF tank cap is blue and clearly marked 'Diesel Exhaust Fluid' with the accompanying ISO standard number or other identifying marks.
There have been a small number of instances where this has happened - although it's difficult to imagine how. In these cases the SCR system had to be drained and no permanent damage was done to the SCR catalysts. If you do accidently fill your DEF tank with diesel, then contact your dealer immediately. Diesel is less dense than DEF and will float on top of the DEF in the tank but even small amounts of diesel can damage your SCR system. So we recommend that you contact your dealer immediately and do not drive the vehicle.
A large part of Diesel Exhaust Fluid (DEF) is de-ionized water do I have to worry about the tank or other parts of the Selective Catalytic Reduction (SCR) system freezing?
DEF freezes into a crystalline slush at 12°F (-10°C) and should not be kept at temperatures above 86°F (30°C). Manufacturers use a variety of heating methods to thaw frozen DEF tanks, including in-tank heating elements. While the thawing process is taking place the vehicle's performance will not be affected (although it may marginally reduce the amount of DEF that is used as a cold engine produces a low level of NOx emissions). In some cases the DEF supply tubes are also heated to prevent freezing, or these tubes are emptied once the engine is turned off.
In short, there is no reason to be concerned about using your SCR truck in cold weather, even in the coldest weather.
Are there any heavy-duty truck manufacturers that don't use Selective Catalytic Reduction (SCR) technology to meet 2010 regulations?
Navistar is the only heavy-duty truck manufacturer not to use SCR to meet EPA 2010 emission standards. Its 2010 models use a combination of Exhaust Gas Recirculation (EGR) and emissions credits earned by meeting new legislation ahead of schedule.
This means that Navistar trucks are allowed to emit NOx at levels above those specified in the 2010 rules up to a limit of 0.5 g/bh-hr.
When was Selective Catalytic Reduction (SCR) technology first used?
SCR technology was first patented in 1957 and has been used for many years to reduce NOx emissions from coal-fired power plants. The technology was first used in vehicles by Nissan Diesel in Japan in 2004 to meet emissions standards that were the strictest in the world at that time. Since then SCR has been widely implemented on diesel vehicles and by the end of 2010 more than 1 million commercial vehicles were equipped with SCR emissions control technology in Europe alone.
How much can I expect to pay for Diesel Exhaust Fluid (DEF)?
The price of DEF will depend on your location and supply method, and the volume of fluid that you purchase. Packaged supply, which comes in 1, 2.5 and 4 gallon jugs, is the most expensive method, followed by 55 gallon drums, 275 or 330 gallon totes and finally bulk volumes which are delivered to directly to fleet terminals. DEF can also be bought at the pump from Pilot, Loves, TA and other travel centers.
The cost saving of moving from jug to tote supply is about $1 per gallon and from tote to bulk a further $0.50. Stay tuned to discoverDEF.com for news about price movement across the different supply methods.
