Diesel Exhaust Fluid (DEF) Management Guide

Diesel Exhaust Fluid (DEF) is a necessary additive that you should refill as often as your regular tank. Because it’s a vital part of using and maintaining any diesel-powered vehicle or machinery, it’s helpful to understand your DEF usage rate and how to tackle problems with your DEF system. H.O. Penn’s DEF management guide provides information on Cat® DEF systems and how to take care of them year-round.

General DEF Management Tips

Your diesel-powered equipment runs on more than just diesel. As diesel goes into your engine, it releases exhaust fumes with nitrogen oxide (NOx) to travel through the Selective Catalytic Reduction (SER) system and out the tailpipe. During this process, DEF gets injected into the SER system to help trap and neutralize NOx into water, nitrogen and carbon dioxide. This effect results in as little emissions as possible being sent into the atmosphere and increased efficiency in your machinery.

DEF collects materials that can be harmful when released into the air, so anyone who uses it should learn the best tips for managing it. Get the most out of your DEF and vehicle by:

  • Choosing OEM- and ISO-certified DEF: Your DEF should fit all standards set forth by the original equipment manufacturer (OEM). In Cat equipment, that means using DEF that meets the requirements from the International Organization for Standardization (ISO), standard 22241-1.
  • Adding DEF when you add diesel: DEF tanks are usually proportional to the vehicle’s diesel tank. When you run out of diesel fuel, you’ll run out of DEF at about the same time. Since you can fill them simultaneously, it’s much easier to keep track of when you need new DEF. Plus, you can find the DEF tank opening right next to the diesel tank opening — just find that blue cap!
  • Not letting your DEF get contaminated: A contaminated DEF tank can lead to various issues, like using more DEF than necessary or corroding the tank. Tank replacements can cost thousands of dollars. Try to prevent them by cleaning the tank opening every time you fill it and using the proper ISO DEF.
  • Storing your DEF properly: When storing DEF, ensure you keep it in a place that does not get direct sunlight. This area should also maintain a moderate temperature to avoid freezing or overheating. The ISO standards provide detailed information about the best ways to store DEF.
  • Know the DEF life span: DEF has a maximum shelf life of about 12 months. If you’re an infrequent user of your diesel-powered vehicles, you may need to drain and change your DEF if you don’t use the full tank within that time. Also, note that DEF only lasts this long in the best conditions. Whether it’s in a tank or storage, if it sits unused through extremely hot or cold temperatures, it will expire much faster. It’s good practice to replace your DEF if it sits through the summer or winter months without use.

Handling DEF in Colder Temperatures

When you operate in areas like New York and Connecticut, the winter months can pose new challenges to your DEF supply.

The freezing point of DEF is 11 degrees Fahrenheit. If your DEF has frozen in the tank, do not try to thaw it using additives because you can damage the entire tank. Instead, simply turn your machine on and wait for the interior heating element to thaw it before operating.

Since DEF has a high water content, it expands when it freezes and can grow up to 7%. If you know the weather will be cold, keep your DEF tank at about three-quarters full or less, giving it room to expand without damaging the tank.

How to Calculate DEF Usage

As mentioned earlier, your DEF tank is proportional to your gas tank. As long as you fill both tanks around the same time, you should be able to avoid running out of DEF. However, if you get off schedule or want a more precise method of tracking your usage, you can use a basic equation.

Most DEF burns at a rate of 2-5% of your diesel fuel. You can ask your dealer what the exact rate is for your equipment or test it yourself. From there, you can multiply your fuel consumption by .02 or .05, giving you an idea of how much DEF you’ll need for a certain job.

For example, if your DEF burn rate is 3%, you’ll go through three gallons of DEF for every 100 gallons of diesel. If you estimate you’ll need 250 gallons of diesel for a job, you’ll need at least 8 gallons of DEF for it to last the entire project.

The Impact of Idle Time

Whether you want to improve fuel efficiency or save money on DEF, it’s important to understand how idling can impact your DEF levels. Aside from using more fuel without moving anywhere, DEF can crystalize or collect soot buildup when your equipment idles.

The more particulate matter that builds up in the DEF tank, the more likely your vehicle will require sudden regens. A regen occurs when the buildup in your tank blocks the system from working as it should, stopping the equipment until it can go through a manual cleaning. This interruption can be a significant concern when you’re in the middle of a job and time is of the essence. The best way to prevent regens is to keep idle time to a minimum and turn off the equipment when you aren’t using it.

Track Your DEF With Equipment Monitoring Services

If you work with Cat equipment, you already know why Caterpillar is the leading brand in industrial equipment. Beyond leveraging quality equipment, you can track vital information, such as DEF levels, with Cat software. Get information on fluid levels, site conditions, equipment history and other data on your entire fleet with VisionLink Fleet Management. Contact us today to learn more about this impressive software or anything else in our catalog of new, used and rental equipment.

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