DEF Fluid Explained

If you own a diesel-powered vehicle or operate diesel-powered equipment, you must have heard about “DEF.” It’s a ubiquitous component of every type of diesel–powered engine used in the United States. It’s essential to understand the role it plays in the operation of your diesel-powered equipment. Without this vital knowledge, you may end up with an engine that does not start up after your next pit stop. Luckily, DEF systems have become pretty user-friendly in the past years due to technological advancement.

What Is DEF Fluid?

DEF or Diesel Exhaust Fluid is a combination of 32.5% urea and 67.5% deionized water. Urea is generated from a byproduct of urine but can be made synthetically for mass-production purposes. The American Petroleum Institute regulates most DEF products.

What Is DEF Used for?

DEF is a major element in activating a chemical reaction that prevents dangerous gases from being produced during diesel operations outside of the environment. The fluid ensures that heavy-duty trucks and other diesel-powered machinery operate within the federal emissions standard set by the Environmental Protection Agency (EPA). These requirements mean that DEF is a valuable substance used in nearly every diesel engine. Diesel engines have been using DEF to accommodate emissions restrictions since EPA created the Diesel Emission Reduction Act in 2010. 

As people become more conscious of climate change and the need to keep emissions low, the demand for DEF will likely increase significantly. DEF is also used in many other industries where diesel equipment is used, such as farm and marine equipment. Since emissions standards have also increased, generators, off-road vehicles, and many other engines have begun using DEF.

How Much DEF Do You Need?

The amount of DEF to use depends on your engine or tank size. Generally, you need 1 gallon of DEF for every 200 gallons of fuel you use. Keep in mind that you should never let the DEF empty completely. You must refill it where there are a few inches left. How often you refill also depends on the miles per gallon and the use of the diesel.

What Happens When You Run Out of DEF?

You should never let your DEF run out because the engine or equipment system won’t allow you to start. For instance, a diesel truck won’t start the engine if it runs out of DEF until you refill the fluid. That means you can easily get stranded if your vehicle runs out of DEF in the middle of the road. Luckily, your vehicle or system will warn you about DEF depletion before it gets to that point.

Where To Get DEF Fluid?

Most fuel stations and auto parts stores sell DEF. You can also purchase the fluid at your nearest big box store. These options are great if you notice you’re running out of DEF. You can also purchase high-quality, affordable DEF from trusted wholesale suppliers.

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