What Does DEF Do?

truck driving down the highway

Back In 2010, the EPA began requiring diesel engines to reduce their production of NOx emissions (i.e. nitrogen oxides) in an effort to reduce air pollution. That reduction was accomplished by using the additive Diesel Exhaust Fluid (DEF). Today, almost all heavy machinery and truck diesel engines utilize DEF to operate within the federal emissions guidelines.

What Happens If Diesel Gets Into the DEF Tank?

Modern diesel engines are designed with selective catalytic reduction (SCR) systems. If diesel gets into the DEF tank, it can cause significant damage to the SCR system. Diesel is a lighter compound than DEF and will float toward the top of the tank.

Diesel engine fluid should never be mixed with diesel fuel itself. These tanks are separate from one another to avoid confusion or accidents during a fill-up. DEF fillers are designated with a small, blue cap. It may be next to the diesel fuel filler or underneath the hood.

Myths About DEF Fluid Busted

  1. Diesel engine fluid is toxic: FALSE
    Diesel engine fluid (DEF) is non-toxic. It does not require any special handling and does not pollute. Additionally, DEF is a non-flammable liquid and non-corrosive. Diesel engine fluid is made from urea, which is a compound rich in nitrogen. Urea is also used in fertilizer, which decomposes. In fact, diesel engine fluid is even more non-toxic than its agricultural counterpart. DEF is injected into the vehicle’s exhaust stream and uses the SCR to convert nitrous oxide into nitrogen and water, which are harmless. Diesel trucks were once seen as dirty. Now, diesel particulate filters (DPF), after treatments, and DEF have made them remarkably clean compared to before.
  2. Vehicles that require DEF get poor gas mileage: FALSE
    DEF vehicles get similar gas mileage compared to other vehicles. They adhere to emission-reducing standards set by the API and EPA. DEF vehicles with CSR technologies offer the best fuel economy with less wear and tear on the engine.

Should I Add DEF to the Diesel Fuel?

You should never add DEF to diesel fuel. In fact, there are two separate places in your vehicle for each. The separate diesel fuel tank and the DEF tank ensure proper, safe storage and usage. If you accidentally put DEF in the diesel fuel tank, the fuel system will need to be flushed. Some repairs and replacements may also be necessary. Make sure you know which tank is which.

What Is the Shelf Life of DEF?

The shelf life of diesel engine fluid depends on how the DEF is stored. DEF should be stored in a safe environment at a temperature above 12° F and below 86° F.  This will extend the shelf life of the product to two years. Storing DEF outside of this temperature range can negatively impact its shelf life. Due to varying standards for storage and safety, it is important to check the shelf life and expiration date on any DEF you purchase.

More information on how storage temperatures impact the shelf life on DEF.

Proper Management of DEF Tanks on Vehicles

Diesel exhaust fluid (DEF) should be regularly topped off to avoid running too low at any point. If the DEF tank is dry, it can significantly impact your diesel engine. Your engine may not turn over until it is refilled. However, safety standards and regulations with SCR technology mean that you will receive multiple indications when your DEF fluid is running low.

How Can I Buy Diesel Exhaust Fluid?

Diesel exhaust fluid can be purchased by individuals in stores across the country. But diesel exhaust fluid for fleets requires higher standards for storage, transfer, and pumping. This helps the fluid stay clean and pure. Retif Oil & Fuel supplies and delivers diesel exhaust fluid in a variety of sizes, including bulk totes that meet all safety standards and regulations.

Learn more about DEF consumption and fuel efficiency with Retif.


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