Best Practices for Avoiding Diesel Exhaust Fluid Issues


Diesel exhaust fluid, or DEF, is a type of emissions control liquid. When injected into the exhaust stream of a diesel engine, it effectively reduces the level of nitrogen oxides (NOx) produced.

This helps those engines meet stringent standards set forth by the U.S. Environmental Protection Agency (EPA). Introduced in 2010, the regulations seek to control the overall amount of engine emissions produced each year.

While DEF is a beneficial, green-friendly solution, it can encounter issues. Today, we’re sharing a few best practices to keep yours in great working condition.

Understanding the Basics of DEF

DEF is comprised of just two ingredients:

  • 67.5% deionized water
  • 32.5% urea

Though it’s clear and colorless, it does have a slight smell. Many people think DEF smells similar to ammonia, or a household cleaning product. The addition of deionized water prevents scaling from occurring within the solution.

When sprayed into diesel exhaust gases, DEF catalyzes a chemical reaction. As the molecules flow through the catalyst filter in the engine’s after-treatment system, they break down existing molecules into nitrogen and water. As a result, the gases transform from harmful agents to harmless ones.

Most modern engines have a DEF indicator level that alerts operators when solution levels get too low. If operators ignore those initial warnings, the engine will start to run diagnostic codes to self-correect. If they still leave the levels unchecked, the engine will begin to shut down, forcing them to refill.

Keeping DEF Clean and Secure

It’s important to keep DEF clean and safely secured. This way, you always know quality levels are high and the solution will work as expected. Here are four best practices to remember as you handle it.

Understand Temperature Restrictions

DEF will freeze if temperatures reach 12 degrees Fahrenheit or lower. While this might be concerning, it isn’t necessarily a problem. Once the liquid thaws out, it will work as expected.

If a machine stays outside all of the time, instances of freezing are bound to occur. While you might not be able to avoid them, you can take steps to maintain the integrity of the liquid.

If possible, try to keep DEF in a cool, dry spot away from extremely hot temperatures. While the cold doesn’t bother it, heat will. Around 95 degrees Fahrenheit, DEF will begin to degrade.

Short bouts of heat are fine, but avoid storing your machines outside in the direct sunlight for the long term. As long as you store the gear in a shady, clean area, you shouldn’t have to worry much about fluctuations in temperature.

Follow Usage Guidelines

For best results, don’t use DEF that’s older than two years old. This is the maximum lifespan that you can expect from a single batch of the solution. If you attempt to use anything older, it could damage the engine.

It’s also important to follow manufacturer requirements when filling up your DEF container. Choose a vessel made of stainless steel or plastic to keep the solution intact. To avoid waste and contamination, you might find it easier to store the solution in smaller containers (such as 2.5-gallon vessels) versus bulk storage.

Keep Dirt Away

Before filling a container with DEF, make sure to thoroughly clean it. Even a small amount of sand, dirt, or grit can change the chemical makeup of the solution. While it will still do its job and change NOx to nitrogen and water, the process won’t be as efficient.

If dirt gets into the engine’s pump or any other component, it can slow it down and impede its operation. That debris can also clog the engine’s filter. In addition to checking the container itself, be sure to give the fill cap a close once-over.

Worried that your DEF might be contaminated? You can use a tool called a digital refractometer to check the exact balance of deionized water and urea in the solution.

If the ratio is off, you may begin to notice several system performance issues, including:

  • A greater degree of DEF consumption
  • Issues with the selective catalytic reduction (SCR) system
  • Engine malfunctions or shut-downs

To avoid user errors, it’s best to hire a DEF delivery service to top off your tanks on a regular basis. Companies like Fuel Logic will take care of the work for you, so you can rest assured it’s right every time.

Avoid Cross-Contamination

This is another common issue that occurs when fill or transfer containers aren’t cleaned the right way. If you’re filling a container up with DEF, make sure there isn’t any residue left behind from a previous solution.

This is especially the case if you’re using the same container to transport both diesel fuel and DEF. If there’s a small amount of fuel left behind in the container, it can become mixed with the DEF solution. When this happens, it can damage many components within the system, including:

  • The pump unit
  • The tank
  • The lines that transport DEF to the after-treatment system

Ensure You’re Using DEF

It might sound like an impossible mistake to make, but some operators have mistakenly filled their DEF containers with diesel fuel instead. Then, they’ve tried to use the fuel in the DEF tank and wonder why it’s not working.

This mixup can cause a range of mechanical and operational issues. If you’re unsure, check the neck shape of the fill container. DEF necks are usually designed in a different shape and color than diesel ones.

Handle and Use Diesel Exhaust Fluid the Right Way

Diesel exhaust fluid (DEF) is a smart way to lower diesel emissions and maintain compliance with EPA standards. However, it’s critical to approach this solution with care and caution.

The above best practices can help you make sure you’re storing, handling, and applying DEF the right way. If you have any questions, refer to the manufacturer’s guidelines when using the product.

Looking for more advice on everything car-related? We have lots of informative guides on our site, so check them out today!

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