What’s the DEF? Proper Handling of Diesel Exhaust Fluid is Critical to Keeping Your Tow Truck Running Smoothly By Jeffrey Harmening
American Petroleum Institute
Maintaining the purity of DEF is essential to keeping your tow truck running reliably.
ue to their husky torque and longterm durability, diesel engines are preferred for hard-working tow trucks. But operators need to be aware that modern “oil burners” can be damaged by using low-quality Diesel Exhaust Fluid (DEF). It can cause problems such as in catalyst poisoning, deposits that restrict equipment from operating, and DEF injector and filter clogging. Even worse, repairs can be very expensive, with long downtime possible and damage that could void the manufacturer’s warranty. These potential problems clearly show why knowing how to handle and store DEF is crucial for a tow business relying on diesel engines. First, though, let’s consider the reason for using DEF. Diesel engines in trucks and other applications sold in the United States must meet stringent U.S. Environmental Protection Agency (EPA) emissions
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requirements. Many of these engines use Selective Catalytic Reduction (SCR) to meet the requirements. SCR is an emissions after-treatment technology that converts nitrogen oxides (NOx) in the diesel-engine exhaust stream into nitrogen and water vapor, two natural components in the air we breathe. Diesel exhaust fluid (DEF) is an essential part of the process. It is injected into the diesel exhaust stream and heat from the exhaust, fluid, and a catalyst convert the NOx into harmless gases. DEF is made from a 32.5-percent solution of urea, with the rest of the mixture consisting of purified water. For the SCR unit to operate properly, the DEF must meet an exacting standard established by the International Organization for Standardization (ISO). This spec ensures that the DEF provides the purity required by diesel engine manufacturers