Do You Know Your DEF?

If you have a Tier 4 or Stage V engine that requires diesel exhaust fluid (DEF), there are some important details that can help you prevent major repair costs or breakdowns.

What happens if you run out of DEF? 

The EPA requires all engines that use DEF to derate and go to idle if they run out of DEF. If you get a low DEF warning on your panel, do not ignore it or the engine will go into a state known as inducement failure. 

If your engine goes into inducement failure, you will need the services of a technician with a tool to reset the inducement counter. In short, it’s best to make sure you never run out of DEF.

Does DEF have a shelf life? 

DEF has a limited storage life. Most information advises that DEF has a shelf life of one year. But that is only true if your DEF is stored in the correct environment. If DEF is kept at a temperature higher than 86°F for a long period of time, it begins to degrade significantly. If DEF is kept above 95°F for a long period of time, its shelf life can be cut in half. 

Though high storage temperatures reduce the shelf life of DEF, cold temperatures are not as damaging. Even if DEF freezes, it remains useful once it thaws. If your DEF has frozen, you don’t need to be concerned about damage to the exhaust after-treatment components. 

Since DEF is mostly water, sunlight can cause evaporation, increasing the urea concentration. Do not keep your DEF in direct sunlight if it is in a clear container. When storing DEF, it is best to use a polyurethane plastic container since stainless steel is the only metal that does not react to DEF.


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How can you tell if DEF is bad? 

DEF should be perfectly clear. Since it reacts to most contaminants, the presence of colors in your DEF indicates that it is contaminated and should not be used. Drain the tank and refill with fresh DEF. 

Another way to identify if your DEF is good is to use a tool called a refractometer. DEF is a mixture of 67.5% water and 32.5% synthetic urea.  A refractometer will inform you if the concentration of urea is still correct.

How can you know if you are buying fresh DEF?

DEF packaging has a date code informing you when it was manufactured. You do not want to purchase DEF that is 6 months old if you are not planning to use it immediately. 

Unfortunately, the date code on Peak BlueDEF is not in plain text. It is written as a series of numbers based on the Julian Calendar. If you need help in reading the code, call us and we will help. There are also a number of resources on the internet that explain the process.

What happens if you use old DEF? 

If you use contaminated DEF or DEF with an inaccurate concentration, you risk damaging your selective catalytic reduction filter (SCR). This can cause DEF crystallization buildup and block your dosing nozzle. This will cause your engine to go into inducement failure. 

Fortunately, your engine has a DEF quality sensor in the tank that should warn you when something is not right. But it is the operator’s responsibility to pay attention to the warning and shut the engine down.

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