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What Happens When Good Diesel Exhaust Fluid Goes Bad

22 Jun 2021 Read time: 5 min

Diesel exhaust fluid (DEF) is required in all Final Tier4 engines, so it’s not uncommon to find it sold at gas stations and dealerships, including RDO Equipment Co. But more than just offering it to customers, RDO Equipment Co. is committed to ensuring all are aware of how to properly manage and care for DEF. If mismanaged, this crucial fluid can become contaminated or degraded, and lead to problems with equipment.

Here’s what happens when good DEF goes bad – and how to prevent it from happening.

First, need to know the basics about diesel exhaust fluid? Read our 10 FAQs and answers about DEF.

When Good DEF Goes Bad – What Happens

Bad DEF can lead to a host of equipment issues, including:
-Increased consumption by equipment
-Loss of DEF effectiveness
-Issues with equipment, including engine de-rating or shut-down
-Potential damage to components, including DEF dosing pump and diesel particulate filter
-Malfunctions with the machine’s SCR system

In the instance of equipment failure or component damage due to bad DEF, the manufacturer’s warranty even may be void, turning these issues into expensive fixes. So what causes DEF to go bad and how can it be prevented? Here are seven key areas.

1. Shelf Life
Because it doesn’t include any preservatives, DEF does come with a shelf life. The good news is, it’s a fairly long shelf life; DEF can usually be stored up to one year without any issues.

RDO Equipment Co. offers DEF in bulk, a great option for large fleets that regularly service equipment and DEF is needed frequently. Smaller fleets, however, should take a closer look at their estimated DEF usage, as over-buying and having it sit too long can result in bad, unusable fluid.

2. Correct Containers
Proper DEF storage enhances its shelf life. It must be stored in ISO-approved containers made from durable composite materials. Because DEF is corrosive to aluminum, storage containers made from stainless steel, polypropylene, and high-density polyethylene are appropriate options. To avoid potential fluid contamination, it’s not recommended to reuse DEF containers, even approved ones.

While it may seem unnecessary, be sure to clearly label DEF and all other fluid storage containers as such. It’s surprisingly not uncommon for someone to mistake DEF for regular fuel or another fluid, and put it into the wrong tank in a machine.

Order DEF

3. Cold Concerns
DEF isn’t harmed by freezing, good news for those who live in colder climates. Because it’s 2/3 water, it begins to turn slushy at 12 degrees Fahrenheit and will freeze solid. One thing to keep in mind is DEF will expand when frozen, so it’s best not to fill containers completely full to avoid damage to them.

After it has been frozen, DEF can be thawed and used with no issues. Don’t add chemicals or additives in an effort to prevent freezing, as doing so may contaminate and ruin the fluid.

4. Beat the Heat
While extreme cold won’t damage DEF, prolonged exposure to heat and sun does present issues. Both can cause DEF to degrade.

50 degrees Fahrenheit is generally considered to be a good temperature at which to store DEF. And even if kept in approved containers in a cool area, direct sunlight is harmful to DEF so ensure it’s stored indoors or in well-shaded areas.

5. Dispensing Guidelines
To avoid contamination when dispensing DEF, keep the container’s nozzle and equipment fill points clean. DEF should only be dispensed directly into a machine, via the nozzle on the storage container. Funnels aren’t recommended, as they can be dirty, therefore presenting contaminates into the fluid. Never transfer DEF into an alternate container, especially one that’s not approved, like a bucket. Even if a bucket is clean, there’s still risk in exposing the fluid to dirt or other contaminates.

Although its name may imply otherwise, diesel exhaust fluid should never be used in a machine’s diesel fuel tank. It should only be used in the designated DEF tank, which features a smaller opening than a fuel tank and a blue cap so it’s easy to identify.

6. Handle with Care
DEF is not toxic, or harmful to humans or animals, nor is it flammable or explosive. While safe, it should still be carefully handled to avoid unnecessary spills, contact with eyes, or accidental ingestion.

In the event of a spill on the floor, cover and contain the spill with an absorbent, non-combustible material such as sand. Shovel and dispose of the material in an appropriate container. If DEF is spilled in a sink, on a vehicle, or on clothes, or gets into the eyes, flush immediately and thoroughly with water.

7. Team Effort
Proper care and management of DEF isn’t just one person’s responsibility; all company team members should be aware of the basics.

It is a good idea to put one person in charge of the DEF care plan, like a fleet manager, who then can educate and remind technicians, operators, and other staff about best practices.

When Good DEF Goes Bad – What to Do
If it’s suspected that DEF has become contaminated or degraded, here’s how to find out and what to do about it.

The easiest way to spot bad DEF is to look at it. The fluid is naturally clear so if it appears cloudy or colored, it’s likely contaminated or old. Contaminates, including small particles or larger rocks or dirt will also be easy to see.

If DEF has gone bad, do not attempt to use it. Dispose of it immediately and do so in an ethical manner. Do not pour DEF down a drain or dump it outside. Every area has proper DEF disposal regulations so check with the local government, municipal, and environmental agency.

Putting forth the effort to properly care for DEF can prevent it from becoming contaminated or degraded, and save more than just the cost of the wasted DEF itself. Following these seven tips is a good starting point to ensure your good DEF doesn’t go bad.


About the Author
Carlos Martinez is Parts Manager for RDO Equipment Co. in Imperial, CA.

For more information on DEF and equipment, including portable dispensing units, pumps and bulk fluid programs, contact your local RDO Equipment Co. store.

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