Frequently Asked Questions About DEF

With the use of SCR or selective catalytic reduction on most diesel engines built in or after 2010, some users may have questions about the use of diesel exhaust fluid. In this guide are some of the most frequently asked DEF questions, as well as some easy answers.

Where is DEF Sold?

Because most diesel trucks and equipment built after 2010 are equipped with SCR, they require DEF. It’s readily available at most auto parts stores and fuel stations, as well as vendors like PEAKHD. For those with large fleets and the ability to store large amounts of DEF, a fuel supplier may be able to help.

How Long Does DEF Last?

The shelf life of diesel exhaust fluid depends on the temperature in which it’s stored. It’s suggested that DEF be stored between 12 and 86 degrees Fahrenheit, but it lasts longer when it’s stored at or below 65 degrees. The experts recommend storing DEF out of the sun and in a climate-controlled facility.

What Happens to Frozen DEF?

While it does freeze at 12 degrees, a vehicle’s operation or start-up won’t be affected by frozen DEF. When an engine starts, the SCR setup heats the DEF lines and tank, which keeps the fluid flowing through the system. DEF is 32.5% urea and 67.5% de-ionized water, which means both components will thaw and freeze at the same rate. Freeze point improvers and anti-gelling additives should be avoided, as they affect the DEF’s ability to perform properly.

How Much DEF Does Equipment Use?

Consumption of DEF varies depending on the equipment’s duty cycle, operation, and environment, but it averages about 5% of the total fuel consumption level. Because most users fill the DEF when they’re getting fuel, that’s what experts recommend. It may also help to keep extra DEF on hand.

What Happens When the DEF Runs Out?

All SCR engines have a gauge that indicates DEF level, as well as a notification system that warns the operator when the fluid is running low. If the tank isn’t filled in time, the vehicle’s speed will be limited until the DEF is replenished. It’s a good idea to have extra DEF on every vehicle that requires it.

While some may see BlueDEF as an unnecessary expense, it does much to keep diesel engines working as they should. With this guide to DEF, owners and operators will know how to keep their vehicles and equipment functioning properly.


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