Is it safe to run that cheaper Walmart DEF?


By Russ and Tiña De Maris

Does your diesel engine require DEF (diesel exhaust fluid)? If it does, you may have heard contradictory information about DEF sources. Some diesel runners will buy only at a DEF dispenser, often at a truck stop. Others swear by “DEF in a box” from places like Walmart, and crow about the significant price break they get. Detractors warn that the label on Walmart’s DEF box doesn’t show that it meets ISO (International Organization for Standardization) standard 22241 and, hence, could be a hazard to use in a DEF vehicle. Should you play it “better safe than sorry”? Here’s the lowdown.

What is DEF? Simply put, it’s water and urea. More precisely, DEF meeting the industry-recognized standard is 32.5 percent urea, and 67.5 percent deionized water. In diesel-fired vehicles, DEF helps reduce certain exhaust emissions. Yes, your DEF should meet the stringent ISO 22241 standard. So when you swing into Wally-World and peruse the automotive aisle, you’ll soon find the SuperTech house-brand DEF next to the “gold standard” Blue-DEF. SuperTech runs nearly $5.00 less than the Blue-DEF when purchased in two-and-a-half gallon containers.

Click to enlarge image. photo.

But wait! The SuperTech DEF label doesn’t show anything about meeting the ISO 22241 standard. This may cause some to shy away from saving money, and glomming onto the more expensive big label stuff. But look at SuperTech’s label a little more closely. Right on the front label, there’s the mark of the American Petroleum Institute (API), loudly proclaiming, “CERTIFIED DIESEL EXHAUST FLUID”. Here’s what the API writes about their program:

“The API Diesel Exhaust Fluid (DEF) Certification Program is a voluntary program designed to certify and monitor the quality characteristics of diesel exhaust fluid intended for use in motor vehicles with diesel engines. Diesel exhaust fluid marketers that have demonstrated that their products satisfy the requirements of the most recent and applicable edition of ISO 22241, Diesel engines – NOx reduction agent AUS 32, may be licensed to display the API Diesel Exhaust Fluid Certification Mark.”

Bottom line: Walmart doesn’t specifically spell out the ISO 22241 standard on their label, but they absolutely MUST meet that standard to get the API DEF certification. Yes, you’re safe saving money buying the “cheaper” stuff and running it in your rig.

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DEF has a shelf life but it is not only limited to time, it is also limited by storage temperature. (and often overlooked at a convenience store, direct sunlight will also degrade DEF fluid. I’ve seen some directly in the sunlight.)

I generally try to purchase at Truck Stops only as they rotate the fluid way more often due the truckers, but I am not afraid to purchase at Walmart or any other store with indoor temps stable at 75-80 degrees. For quality reasons, I try to find fluid that is 6 months old or less if stored in a temperature controlled environment not subject to window exposure.

As a general rule, DEF will last 1 year on a shelf. Some say 2 if kept under 77 F. And some say if under 50 F, it can last up to three years. Over 87 F, then expect the fluid to last 2 months. I would never trust that. Who knows where it was moved over that time period? I would not care about the dust on top. Just verify the date code first and consider the storage medium temps second. Also check for direct sunlight exposure on the shelf.

They APi label is important for quality but is on almost every brand bottle at Walmart.

I have a 2014 Ram Dually. I used to keep the DEF tank plum full to the brim. Per the RAM Service Center (they recently replaced my DEF pump at just under 100,000 miles for $2800), do not overfill the DEF tank. Do not let the pump go under 1/4 tank from empty. The DEF fluid keeps the pump cool when submerged. The DEF Tank needs air on top (I don’t remember why he said so but it does). The service mechanic states that when filling the tank, watch the gauge. When it shows “FULL”, stop. I wish this had been in the service/owner’s manual….Generally, when I get to a 1/4 tank, I add 2.5 gallons and call it good. It just hits the FULL level.

M. Will

DEF has a shelf life. There is a code on the bottle or container that will let a person know when it was manufactured. If you Google DEF you can find out all about this shelf life. If I were putting this stuff in my diesel truck then I would surely want to make real sure that I knew when it was manufactured. It costs a lot of money to find out that the DEF you have been buying and putting into your truck has just cost you a ton of money!!

Steven Scheinin

I have been using Walmart Super Tech DEF in my RAM 3500 for 4 years, with no problems.

Steven N.

I went in and looked at the two brands of DEF on the shelf at Walmart. Based on what I had read about age, temp, etc, when I found the containers with a noticeable amount of dust collected on the top I turned and walked away. I don’t buy often enough to feel the need to keep a jug around so when my truck starts nagging I just stop at a truck plaza and top off the tank. The price at the pump is cheaper in my area also


I don’t use Walmart DEF because the seal is too easy to tamper with. I bought one where the seal came off with the cap. There are known cases of people using the DEF and returning the container, filled with water, to get a refund. I’m not taking a chance.

Hoss Smith

Using DEF? If so read up on its storage and handling requirements. We bought a DEF tester and have found DEF that was unusable either due to heat or age so now it is stored in a temperature controlled room and we only keep a small amount on hand.


I disagree with this article. Right after putting walmart DEF in my 2011 GMC, the truck threw an error code that there was a problem with the DEF system, requiring service within 200 miles or I get put into limp mode. After a day and a half it was determined that the item that sprays the DEF into the system was clogged and needed replacement. All was covered by warranty. Maybe a coincidence maybe not. I stay away from wallyworlds stuff now. I was in the middle of Illlinois and took the better part of 150 miles to find a dealer that could work on my truck. I don’t care to sweat bullets again like that. The extra few bucks are cheap insurance.

Primo Rudy's Roadhouse

I have heard that we need to be careful about the date of manufacture for DEF. I usually buy the Blue DEF from Auto Zone, or even our grocery store. The last time I looked at Wally-World, their DEF boxes were disintegrating on the shelves.


I prefer the pump than lugging 20 lb. boxes around. It’s usually cheaper and more convenient. If I have to buy a box of DEF, I’ll buy whatever is on sale. Having retired from the auto parts manufacturing industry, I know that most store brands (and even some OEM brands) are all made in the same factory. Walmart or most any other retailer that has a house brand doesn’t have the time or resources to manufacture their own stuff.

That said, their buyers would be hung from their thumbs if they bought something like DEF that didn’t meet any accepted industry standards. Sure, you can find products that have been mistreated in a truck or warehouse. A brand name isn’t protection from that.


Actually, Walmart sells BRAND NAME BLUE DEF! I just bought some the other day! I don’t like buying the 2.5 Gallon Boxes at Walmart, because it is SO expensive. I usually buy my DEF in Bulk at Truck Stops, a whole lot cheaper.