DEF: Here to Stay

If you're new to the diesel exhaust fluid required by today's engines, here's what you need to know.

June 2013, - Feature

by Deborah Lockridge, Editor-in-Chief - Also by this author

SHARING TOOLS        | Print Subscribe
TravelCenters of America’s DEF dispensers, which it calls the “DEF+1,” pump both diesel fuel and DEF and are available at nearly all locations. Drivers can authorize diesel and DEF transactions at the same time at the same dispenser, pump both products in any order, and pay for both fills at the same time.
TravelCenters of America’s DEF dispensers, which it calls the “DEF+1,” pump both diesel fuel and DEF and are available at nearly all locations. Drivers can authorize diesel and DEF transactions at the same time at the same dispenser, pump both products in any order, and pay for both fills at the same time.

In 2007, as many truck and engine makers started announcing they would use selective catalytic reduction to meet 2010 federal emissions regulations, a new term entered our trucking dictionary: diesel exhaust fluid.

As we soon learned, SCR is an aftertreatment technology that injects small amounts of DEF, a water-based solution containing urea, into an engine’s hot exhaust stream to reduce emissions of nitrogen oxides (NOx).

In the exhaust, DEF vaporizes and forms ammonia and carbon dioxide, explains Mark Ulrich, director of customer support for Cummins Emissions Solutions. When the exhaust gas and ammonia are then passed over a catalyst, NOx is converted into harmless nitrogen and water.


DEF is a necessity to make this happen. Kept in a separate reservoir tank from the diesel fuel, it’s a solution of 32.5% high-purity urea mixed with very high-purity water. Urea is an organic nitrogen-containing compound commonly used in agriculture as a fertilizer.

However, you can’t just buy fertilizer and make your own DEF. The urea used to make DEF is known as automotive grade or environmental grade, a higher grade than the kind used for fertilizer.

Although it meant a new technology and a new fluid to deal with, the good news was, SCR meant fuel savings. Because engineers no longer had to optimize the in-cylinder combustion process for NOx control, they instead were able to tune the engine for better fuel economy.

Manufacturers and suppliers were soon meeting to discuss developing an infrastructure to distribute DEF. There was controversy as Navistar International, which was attempting to develop an emissions solution that did not involve the add-on liquid, claimed DEF would be expensive, hard for drivers to deal with, even toxic.

With Navistar’s decision last year to go the SCR route after all, it’s clear that DEF is here to stay.

“The naysayers were those who originally wanted to go with a non-SCR technology,” says Frank Cook, senior vice president of new product development at Old World Industries, which sells Peak BlueDEF. “In reality the engines and systems are running better with SCR (and less EGR) and drivers have gotten used to DEF quickly.”

Brian Hoover, national sales director of DEF at Mansfield Oil, notes “any time there is a change or a new product to be monitored and managed by the driver community, there will be some resistance. However, we see a general acceptance that has been adopted over the past 24 months, and DEF is becoming more of a common practice of implementation.”

However, drivers and fleets new to SCR typically have questions about DEF relative to storage, safe handling and availability.

Availability and price

There are almost three quarters of a million Class 4-8 SCR-equipped vehicles on the road in North America today, according to Integer Research, the leading DEF market analyst.

DEF consumption in North America by Class 4-8 vehicles is expected to reach 204 million gallons by the end of the year, according to Ed Wells, director of sales, Air1, for DEF supplier Yara North America.

Integer predicts this will double to 402 million gallons by 2015.

Truckstops, truck dealers, aftermarket parts stores and other outlets carry DEF in 1-gallon and 2.5-gallon containers. A growing number of truckstops carry it at the fuel island. In fact, the number of truckstops offering DEF at the fuel island topped 1,000 earlier this year.

Pilot Flying J accounts for over a third of the DEF pump network, offering it at more than 3,000 lanes, followed by Love’s and TravelCenters of America.
In addition, many fleets have chosen to use 55-gallon drums, 275-gallon or 330-gallon totes, or other bulk supply options for their own facilities.

Jeff Lewis, vice president of sales for Airgas Specialty Products, which sells AiRx DEF, explains that there are only a handful of companies that actually make urea. It’s a very capital-intensive process, requiring billion-dollar facilities. Instead, many companies that sell DEF buy dry or concentrated urea and “solutionize” it with high-quality water to meet ISO standards.

The per-gallon price for DEF is highest in jug form, according to Integer’s DEFโ€ˆTracker, running about $6.25 per gallon as of April. At the pump, the price was running an average of $2.79, while tote refills were 27% less at $2.04.

“Going beyond totes, getting into permanent storage units of 1,000 or more gallons, they can really get a better price at that point,” says ChrisGoodfellow, an analyst with Integer Research.

“North America has historically enjoyed a surplus in production of DEF,” notes

Cummins’s Ulrich. “It’s reasonable to expect DEF prices to remain steady, or potentially even decline, due to free market completion and abundant retail infrastructure.”

On the other hand, urea also is a publicly traded commodity subject to fluctuations, as crude oil is. The biggest driver in that marketplace is fertilizer, so there could be seasonal fluctuations in the price based on projections of what’s going to happen in the agriculture business.

Handling and storage

The biggest concern in handling and storage is contamination, followed by the slight corrosiveness of DEF. Equipment used for DEF needs to be dedicated, both to address contamination concerns and because DEF will corrode some metals, such as copper and brass. That’s why DEF tanks on trucks are plastic.

Totes like this one offer about a 27% savings on DEF over the pump price. Bulk options can mean even more savings.
Totes like this one offer about a 27% savings on DEF over the pump price. Bulk options can mean even more savings.

“While DEF does have a pungent aroma similar to that of ammonia, it is a non-toxic, non-polluting, and non-flammable substance that is safe to handle and store and poses no serious risk to humans, animals, equipment or the environment when handled properly,” Ulrich says.

You do need to keep DEF in a temperature-controlled location and out of direct sunlight.

High temperatures will shorten the life of the product, and DEF does freeze at about 12 degrees. However, freezing doesn’t harm the product or the engine, and SCR systems are designed to deal with DEF that may be frozen or slushy when the truck starts up, explains Thomas Kalagher, product development manager for Prestone Performance Chemicals, which earlier this year introduced its Command brand of DEF.

Airgas’s Lewis says DEF does have a tendency to crystalize when it get exposed to air. “It almost looks like frost, but it’s just crystallizing. It also has a tendency to creep a little bit, but regular care and maintenance will take care of a lot of that.”

Despite concerns that DEF can “go bad” quickly, Hoover says, “DEF will be just fine for years when stored properly.”

The importance of purity

When you do hear of problems with DEF, the culprit is often poor quality or contamination. Buy from a reputable source that is API registered and meets the ISO 22241 standard. Beyond that, different brands of DEF all basically work the same.

“Impurities can cause premature failure of the catalyst, and that can cost $8,000 to $15,000 to replace,” says Prestone’s Kalagher.

“There’s some risk if you’re not buying from a reputable source just to save a penny a gallon.”

“Based on what we’ve seen in Europe and the U.S., we know that 80% of contamination happens at fleet terminals,” says Yara’s Wells.

To safeguard against DEF contamination, he recommends a few simple tips:

1. Keep DEF away from materials such as fuel, oil, grease, water, dust, dirt, metal and detergent.

2. If the DEF fueling equipment at your terminal needs to be cleaned, rinse it with de-mineralized water - NOT tap water.

3. Only use dedicated DEF equipment for storing and dispensing DEF. Do not use funnels or bottles that have been used for other fluids.

4. While a DEF pump’s magnetic guard will prevent you from accidentally putting DEF into the wrong tank, be sure to insert the DEF nozzle into the truck’s DEF inlet to avoid contaminating the spout.

5. Do not refill previously used DEF containers, as they may be contaminated.


  1. 1. Craig Hummel [ April 01, 2014 @ 09:14AM ]

    I purchased a 55 gallon drum of Air-1 it is stored out of the sun underneath a porch on the north side of the house. Myself and two friends just purchased new Dodge diesels, and are sharing the DEF. I purchased a plastic rotary pump to extract the DEF as we needed it. After each use i suck water through the rotary pump and hang it up. After reading this article i should make some adjustments, use demineralized water for cleaning the rotary pump and use the demineralized water to rinse the two gallon container we use to refill the truck. Are we at risk of destroying our equipment.

  2. 2. Fred Bosslman [ October 12, 2015 @ 07:17PM ]

    I was told that soon there will be an additve or a pill to add to water so it will not be nessasary to have the unsulated tanks and dispensers? Any truth to that?

  3. 3. Richard [ October 22, 2015 @ 09:04AM ]

    Equipment for d e f needs to be dedicated? That mean only use it for d e f? What about equipment not used much or in semi storage? All this is bullshit anyway and any productive person knows it

  4. 4. Richard [ October 22, 2015 @ 09:05AM ]

    What about stored and occasional use equipment?

  5. 5. Gopal s Singh [ December 31, 2015 @ 09:07AM ]


  6. 6. Jimmy clause [ February 03, 2016 @ 04:21AM ]

    DEF is my Biggest problem in my company all my breakdown are caused of this . Sorry it is Bullshit and my mpg is way down please somebody tell me when I can buy a new truck . Because it also is my Biggest headack .Breakdowns and such . So much money wasted . So much work lost . Only so many days in a month . And there is know way with all the wast of jugs and process to make Def . ETC . Out ways the benifits and so many people are breaking down with new Vehicles . WHY???????????!!?!!!!!!!!! So frustraited !!!!!!๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜๐Ÿ˜ฌ๐Ÿ˜ฌ๐Ÿ˜ฌ๐Ÿ˜ฌ๐Ÿ˜ฌ

  7. 7. PETER N KLASSEN [ February 09, 2016 @ 09:02AM ]

    Jimmy I totally share your frustrations. I bought a a new truck in the hope of saving money...however it seems like it was in the shop almost every week related to the DEF system problems. On top of the breakdowns Volvo has the power to DERATE your truck so you can't drive it . The DEF system has been the biggest cause of lost profit in my trucking career!!!!

  8. 8. David C [ March 10, 2016 @ 01:13PM ]

    Last winter my DEF light came on. So I put 2.5 gals in and the next day it came on again. I took my truck to the dealership. They told me the DEF tank froze and ruined the sensors and the tank had to be replaced. I said, wait a minute. You are telling me it froze in Texas? What if I lived in Montana? What the hell would I do then, replace it every year? Personally I think DEF is just another way to get a little more tax money out of us.

  9. 9. Diesel shop owner [ April 15, 2016 @ 08:51PM ]

    Lol @ this article. DEF is the single biggest mistake in the history of diesels. 80% of all trucks with def experience def and regen breakdowns repeatedly. Def issues have become the #1 repair in our shops. Your pathetic greed that's good for nothing but lining your pockets with money will go down in history as the worst possible mistake ever!

  10. 10. Jon [ May 14, 2016 @ 01:22PM ]

    Just put 2.5 gallons of Peak DEF in my 12 F250 cause had been on. It is still on???????? Confused I am......

  11. 11. Darrin [ June 25, 2016 @ 10:03PM ]

    Def is a crock of crap.its the worst thing that's happened to trucking since elogs.i have spent nearly 10 grand replacing all my dpf components.its all a money grab by the government and is lobbyists.i can wait til I delete this crap off my motor.the mpg will be better it's a proven fact.the lie that has been sold to use is just that a lie.its not better for anything but the butt wipes that produce it.

  12. 12. Bret P Goss [ September 07, 2016 @ 02:43PM ]

    DEF and dirt don't mix! They person that makes DEF is in a laboratory, by a person in a lab coat. Kept pure, then dispensed by someone wearing coveralls and work gloves! That's why I invented the DEFBooty. Simple, economical, effective!

  13. 13. Ernie Kelemen [ September 18, 2016 @ 12:55PM ]

    This def stuff is for the rich to get richer because anyone that has used this crap no that the millage is 2/3's of the older engins and the brake downs will kill small trucking companys because you have to have spare trucks. More regulations we don't need you god dam tree hugers How much more do we have to take, me nun i had to lay off 20 people and sell my rig moving trucks that i ran 42 years, not good.

  14. 14. alex [ October 02, 2016 @ 10:46PM ]


  15. 15. Oscar Yeager [ November 17, 2016 @ 04:51PM ]

    Everything in this article is wrong. Us drivers HATE DEF and other emission equipment with a perfect passion. The big secret nobody wants you to know is that by and large, diesels don't pollute anyway, since even back when you had mechanical engines, almost all exhaust is particulate matter, mostly soot, that very quickly falls out of the air and down on the ground where it is virtually harmless. No different than emptying your coal furnace ashes out onto the ground where it belongs.

  16. 16. Matthew Porter [ December 03, 2016 @ 02:46PM ]

    I have never met any driver, or owner, that has a single good thing to say about DEF. 15 years of being a diesel mechanic, I can tell you first hand, DEF damages trucks. Period.
    Don't take my word for it though, go pour some pig piss in your BMW or RR fuel tank, and let me know how that works out for you.
    Someone devised a way for themselves to get rich, and a way to take out some trucks, as too many are flooding the US, so instead of manufacturing less, they will just make them not last as long.


Comment On This Story

Comment: (Maximum 2000 characters)  
Leave this field empty:
* Please note that every comment is moderated.


We offer e-newsletters that deliver targeted news and information for the entire fleet industry.


Sleeper Cab Power Experts

The expert, Steve Carlson from Xantrex, will answer your questions

View All



The expert, Brian Fletcher from Eaton, will answer your questions

View All


PC-11 The New Engine Oils Experts

The expert, Shawn Whitacre from Chevron Delo, will answer your questions

View All