Managing your diesel exhaust fluid (DEF) is an important part of managing your fleet of trucks, whether you have just a couple of trucks or a couple of hundred. You need to make sure you source and supply enough DEF for the trips your drivers need to make, or budget the appropriate amount for them to fill up as needed.
In this short guide, you’ll learn what DEF is and what trucks in your fleet may need it. You’ll also learn what it does for your trucks that require it, and what consequences your choice of DEF may have for your fleet.
What Is DEF Fluid?
Diesel exhaust fluid was developed to reduce air pollution from diesel engines and help them meet emission standards when used with a Selective Catalytic Reduction (SCR) System. SCR systems have been standard on most medium and heavy-duty diesel vehicles since 2010.
If your truck has an SCR system, it will inject DEF into your exhaust as you drive. The DEF interacts with your exhaust to chemically convert toxic nitrogen oxides into harmless nitrogen gas and water vapor. You’ll learn more about how that process works in the next section.
Any SCR truck will have an independent tank for this fluid. You and your drivers will need to keep it filled to a level sufficient to operate the engine. Large trucks and heavy equipment may hold anywhere from 5 to 50 gallons of DEF. To really understand the importance of DEF fluid, it can be helpful to understand what happens inside your engine.
What Does DEF Fluid Do?
DEF fluid is designed to make your diesel engine’s emissions much safer. This is made possible by some new technology and an interesting chemical reaction. DEF is composed of an aqueous urea solution made with 32.5% urea and 67.5% deionized water. This mixture is injected directly into the hot exhaust through the SCR.
The SCR brings the two forces into contact. The heat from the exhaust causes the exhaust fluid to break down into ammonia and carbon dioxide. When these react with the toxic nitrogen oxides in the exhaust, they are all converted into nitrogen and water vapor.
Modern diesel engines do not operate without diesel exhaust fluid. You cannot go without DEF even if you aren’t concerned about the ecological advantages because the engine will most likely not operate without DEF.
When most modern diesel engines detect that DEF levels are too low, engine power will be locked down, and your maximum speed will be restricted. If you power down the engine while your DEF tank is empty, you will often not be able to start the truck again until enough DEF is detected.
There are good reasons for your truck engine to lock down when there isn’t enough DEF available. Running your diesel engine while the DEF tank is empty can cause crystal deposits to form in the selective catalytic reduction system. Repairing this problem can be costly.
You’re not just saving the planet by keeping your trucks stocked with DEF; you’re also likely to save money. In modern diesel engines, DEF is projected to deliver 3% to 5% better fuel economy compared to older-style diesel engines without an SCR system.
Is All DEF Fluid the Same?
Not all DEF fluid is the same. The chemical formula is the same across products because the correct formula is necessary for SCR systems (and required to satisfy all requirements set in ISO 22241). All brands must also have the correct chemical formula to be sold with API certification.
While all brands adhere to the required formula, their fluid quality may differ. Compliant store brands operate as well as premium fluids when they’re fresh, but cheaper blends may have a shorter shelf life.
If you want to make sure DEF of any grade stays better longer, store it properly and protect it from contamination. You’ll want to keep the containers out of direct sunlight and UV exposure, and maintain temperatures that prevent the fluid from spoiling.
Any DEF you store on site should be kept in a well-ventilated area with temperatures between -5°C and 25°C. If DEF ever rises above 25°C, its shelf life will drop. If it reaches any temperature above 35°C, its life is reduced to just a few months.
DEF can also be contaminated if stored improperly. Make sure you keep any onsite DEF sealed against dust, dirt, and moisture. Do not refill old DEF jugs, and do not use any funnels, hoses, or containers that have been used for other fluids to fill a DEF tank.
Contact HOLT Truck Centers to Explore More about Trucks Today
You now understand what DEF does for your trucks, how it works inside your engine, and how it can help you save money on fuel. You have many options for DEF, and making the wrong choice could have consequences.
If you need help keeping your fleet in top condition, you can find new and used trucks, parts, services, and more at HOLT Truck Centers. Call your nearest location today to discuss your needs, schedule an appointment, or learn more about how we can help. We look forward to hearing from you!
