Tuesday, February 7, 2023


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. walmart.com 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.


Facebook Groups you might like
RV Electricity
RVing with Dogs
RV Tech Tips
Electric Bikes for RVers
RV Advice
RV Short Stops (NEW)
Towing Behind a Motorhome
. . . and the official RVtravel.com Facebook page

Winterizing your RV this season? Amazon has a wide choice of RV antifreeze.


0 0 votes
Article Rating
Subscribe to comments
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
Jesse Crouse
8 months ago

Our 2006 Tiffin40QSH DP is looking real good now. The Cat C7 runs clean and purrs like a kitten. Fortunate to have a Heavy truck shop 3 miles from the house and they can fix anything at a reasonable price. Will run the coach till the wheels fall off or my wheels go bad. And by the way California you got crossed off the list of places we would visit and the same to any states with the same rules.

2 years ago

I buy bulk DEF at a Pilot less than 100 yards from the local Walmart and the price for 2.5 gals at Walmart is exactly the same as the bulk at Pilot. $6.97. I would rather buy bulk at a major truck stop – at the pump – I know they turn product

Larry H Lee
2 years ago

No more Walmart DEF for me after finding several seals clearly removed and replaced. Who knows what got put in those containers.

Bob P
2 years ago

As a post script you should not buy DEF in large quantities at a time as it does have a shelf life, so buy it as you need.

Wayne Caldwell
2 years ago

When my DEF gauge reads 1/2 full, I top it off with another 2 1/2 gallon jug (usually the Wal-Mart stuff). So whatever is already in the tank is updated and refreshed every couple of weeks.

Billy Bob Thornton
2 years ago

Lots of info on shelf life. In reality, I’ll bet dollars to donuts nobody sucks the “aged def” from the reservoir. Besides, every time you add more DEF, and if it’s from a newer batch the ageing chemistry changes the shelf life date. This whole discussion is circular, with no definitive answer, other than, yep, it has a shelf life.

2 years ago

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.










2 years ago
Reply to  TravelingMan
Billy Bob Thornton
2 years ago
Reply to  TravelingMan

So, if it is in your DEF holding tank longer than some of the recommendations then what. In practicality, it’s in there till it’s injected, period.

M. Will
3 years ago

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
3 years ago

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

Steven N.
3 years ago

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

3 years ago

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.

3 years ago
Reply to  Kim

this is a very real possibility the same with oil containers, trust a dirt ball you will eventually get burned. The girl at the return desk said they try it all the time and just say their husband told them to return it and then they just walk away, no kidding.

Hoss Smith
3 years ago

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.

2 years ago
Reply to  Hoss Smith
3 years ago

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.

3 years ago
Reply to  Tom

Have only used the cheap stuff from Wally World on our diesel pusher for the past 6 years…not a problem, yet. Have also filled DEF up at major truck stops, but our DEF tank is on the wrong side at the truck stops…found the smaller containers to be more convenient.

Ron Lane
1 year ago
Reply to  Robbie

I have the same problem with the DEF tank being on the passenger side. So I too, use the WM stuff almost exclusively since 2013. Unfortunately, the flexible spout on the WM DEF containers is not quite long enough to reach my tank without spillage, so I came up with a funnel and tube that I can attach to the compartment door that allows me to empty the container without spilling a drop.

Primo Rudy's Roadhouse
3 years ago

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.

3 years ago

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.

3 years ago

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.

3 years ago
Reply to  Jeff

I don’t know who makes WalMart’s DEF, but I’ll bet heavy money it isn’t WalMart. More likely the same outfit that makes the Brand name Blue Def. When I’m on the road, I buy by the gallon at truck stops, but I don’t have any trouble buying WalMart’s DEF. Used for 6 years w/o a problem. I’m in complete agreement with Michael, WalMart doesn’t make their own DEF.

Bob P
2 years ago
Reply to  Nicholas

Walmart doesn’t make anything they sell, they are retailers not manufacturers.

Subscribe to our newsletter

Every Saturday and Sunday morning. Serving RVers for more than 20 years.