Your DEF Questions Answered.

After last week’s inaugural installment of the ABCs of Diesel, some of you had more questions about DEF (diesel exhaust fluid).

How do I store it?

“Think of DEF like you would a gallon of milk. You wouldn’t throw a gallon of milk in the bed of your truck, leave it there for months, and then drink it. Like milk, DEF is mostly water, so it requires a little extra care.” – David Robinson, Service Manager at Country Truck & Auto

DEF should be stored in a cool, dry, well-ventilated area, out of direct sunlight. The optimum storage temperature is up to 77 °F; however, temporary exposure to extreme temperatures has little to no impact on the quality of DEF. The shelf life of DEF is dependent on the storage temperature. DEF will degrade over time depending on temperature and exposure to sun light. If stored in perfect conditions, it can last up to 2 years. In the real world, you can expect that its shelf life to be about one year from the manufacturer’s date on its label.

For small amounts of DEF, David Robison goes on to say that it “has been our experience that once you open a container of DEF you either need to use all of it or throw it out. Shelf life of the DEF, once the container is opened, seems to diminish much more quickly. The cost of a new container of DEF is very small in comparison to the cost of repairs if poor quality/contaminated fluid is used.”

Because DEF is comprised of 67.5% water, freezing and evaporation could occur. DEF will freeze in temperatures of 12°F or lower. Keep in mind, when frozen, DEF will expand. As far as evaporation is concerned, this is less common. Cummins field tested vehicles across the US in high temperature locations and found that significant amounts of evaporation that would impede engine performance or operation did not occur. To be on the safe side, keep the cap of the DEF tank and storage containers securely closed.

In the off chance that your DEF concentration is not correct, your SCR (selective catalytic reduction) system will recognize the issue. Your DEF warning light will turn on and your vehicle will require service, because the DEF tank will need to be drained.

Should I be concerned about handling DEF?

DEF is a stable, nontoxic, nonpolluting, non-hazardous, and nonflammable solution. According to Cummins, DEF poses no serious risk to humans, animals, equipment, or the environment when handled properly.

What should I do if I spill DEF?

If DEF is spilled on your vehicle, rinse it with water. If you spill in your driveway, garage or shop, use sand to contain/absorb the spill and then shovel the mixture into a suitable container for disposal. Try not to pour DEF into a drain, because it is corrosive to copper and PVC plastic, which is what your pipes are made of. If spilled into a drain, flush thoroughly with water. For significant quantities (think several gallons or more), contact local authorities for proper disposal procedures.

Can I make DEF myself?

NO! The 32.5% urea (ammonia) concentration is critical. Unless you have an advanced degree in chemistry, buy it at your local auto parts store or truck stop. Your SCR system can tell the difference between your home-brewed concoction and the real deal. It will trigger the DEF warning light and your vehicle will likely need to be serviced.

Winter is coming and I am worried that my DEF will freeze in my truck, can I add an anti-gelling or freeze point improver to the DEF to prevent that?

No. Again, maintaining the proper urea concentration is a factor. Additives are not recommended for use in DEF and can potentially cause your truck to have performance or functionality issues.


Still need help with your DEF fluid, call our experienced technicians at the County Truck Service Center!



Written by:

Beckie Bean

Digital Content Coordinator at Country Truck & Auto

September 29, 2016

Source: Cummins

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