How to Use Refractometers with DEF

If you use diesel exhaust fluid (DEF), you’ve probably heard of refractometers. These tools are an essential part of making sure that the DEF you’re using is of quality so you can get the appropriate amount of NOx (Nitrogen Oxide) reduction to meet the requirements set by the Environmental Protection Agency (EPA).  Since all diesel engines manufactured post 2010 requires a Selective Catalytic Reduction (SCR) system, the refractometer has been a mainstay for anyone who services diesel engines and needs to measure the quality of DEF before usage.

Why It Matters

DEF is a mixture of environmental grade urea and deionized water, and when injected into the exhaust system of a diesel-powered vehicle it services to reduce NOx emissions, which have been shown to be harmful to the environment. The key, though, is that you need to use DEF that meets spec or it won’t provide the emissions reduction that’s required by the EPA and quite possibly shut down your system.

Verifying DEF Purity

Refractometers are not a new tool—they’ve long been used as a way to measure a number of things in a variety of industries—but now they come specially designed to measure and test diesel exhaust fluid.

A basic refractometer consists of a prism, cover plate, correction screw, mirror tube, and an eyepiece. These portable tools allow a user to determine the precise level of DEF and its purity by taking a liquid sample and placing it on the prism. Light that passes through the sample bends (refracts) according to how concentrated the liquid is—more concentrated means more refraction. Peering through the magnified eyepiece, you can determine if the refraction levels meet the requirements for DEF.

In order to work properly, a refractometer must be focused and calibrated, a process you can achieve by putting a couple drops of pure water on the tool. After it’s calibrated, you can place a couple of drops of DEF on the prism and determine, based on where the bottom of the shadow line intersects with the scale, whether you have the correct amount of urea, more is needed, or the concentration is too high and it must be diluted.

A digital refractometer, which Certified DEF offers, consists of a handheld device that offers a number of different scales for a specific fluid.  By placing a sample of the fluid with a pipette on the measuring surface and closing the evaporation cover and pressing the “Go” button a test result will appear in the window within a few seconds.  It’s recommended to take an average of five tests to verify the most accurate reading.

Just make sure to always treat it like a precision tool and use and store it as directed in a clean and dry place until its next use to ensure accurate readings moving forward.

Since most DEF comes in premixed containers, a problematic sample with the refractometer would likely indicate that either the DEF is low quality, or it has become contaminated during storage or transport. Contaminated or low quality DEF must be drained entirely and the container washed out by a professional before being refilled with only high quality fluid from a place like Certified DEF.


Tips for Handling and Cleaning DEF

Tips for Handling & Cleaning DEF

All post 2010 medium and heavy-duty diesel engines are required by the Environmental Protection Agency (EPA) to use diesel exhaust fluid (DEF) to reduce the amount of harmful emissions in the atmosphere. DEF is a mixture of two-thirds deionized water and one-third environmental grade urea, which is released into the exhaust stream and breaks down harmful NOx emissions into nitrogen and water, both of which are harmless and currently reside in the air we breath.

There are a number of misconceptions about DEF, but perhaps where the confusion lies is in the handling and disposing of the fluid. Fortunately DEF is a non-toxic material that doesn’t require special handling other than to safeguard against contaminates. It’s non-polluting, non-flammable, and non-hazardous. Here are some tips on how to properly handle and clean DEF.


If DEF spills, it can easily be wiped up without a problem. If you have DEF that comes in contact with skin, wash area with mild soap and water. Avoid direct contact with eyes and rinse thoroughly with water if contact occurs.

A bigger issue when dealing with DEF spills is contamination of the fluid itself. Since it’s sensitive to chemical impurities and must maintain accurate specs to properly function with the Selective Catalytic Reduction system, it’s important to handle with care, ensuring that it doesn’t become contaminated.


DEF has a shelf life of roughly two years if stored in moderate temperature and away from direct sunlight. However, if stored in varying temperatures the shelf will decrease but will not degrade the fluid.

DEF has a freeze point of 12 degrees F, the 32.5% solution ensures that the fluid freezes and thaws at the same rate preventing over concentration or dilution of the product. Industry packaging and tanks have also been designed for expansion of frozen fluid.

If stored in temperatures above 90 degrees F., the shelf life decreases to roughly one year, but the product will continue to maintain its quality.

Preventing Contamination

As mentioned above, the biggest risk with DEF is that improper handling could cause contamination. When storing or transporting DEF, it’s important that you use only containers that are DEF dedicated and have not been used for other fluids. The same is true for tanks, pumps, hoses, and nozzles that you plan to use to dispense DEF. You can store diesel exhaust fluid in stainless steel and plastic containers, but avoid storing it in carbon steel, copper, copper alloys, or zinc-coated steel containers.

When you purchase DEF, make sure it’s from a company that adheres to the ISO 22241 standards as well as has met the guidelines set by the American Petroleum Institute.

7 Things You May Not Know About Diesel Exhaust Fluid

In 2010 the Environmental Protection Agency (EPA) began requiring all newly manufactured medium and heavy-duty vehicles to cut harmful emissions. With the selective catalytic reduction (SCR) system and the use of diesel exhaust fluid (DEF), the industry has been able to drastically reduce NOx and particulate matter (PM) since then. Even if you’ve used DEF before, here are a few things you might not know about it.

1: DEF Is Made of Urea and Deionized Water

The American Petroleum Institute (API) carefully regulates the production of diesel exhaust fluid, which is a mixture of roughly two-thirds deionized water and one-third environmental grade urea, which is a synthetically derived product.

2: DEF Availability

DEF is available throughout the United States but it’s best to purchase it from a trusted source, such as Certified DEF, to ensure that you’re getting a high quality, contaminate free product that’s API Certified.

3: DEF Can Add a Lot to Your Truck

SCR-equipped vehicles have reported better fuel efficiency, and more power. They also yield a harmless nitrogen/water mix instead of harmful NOx and PM emissions into the air.

4: DEF Is Beneficial for the Environment

Studies have shown that harmful emissions are linked to a number of health issues, including but not limited to, respiratory and lung function, cardiovascular diseases, and asthma. Adding DEF to your SCR system turns harmful emissions into nitrogen and water, which are already naturally present in the air we breathe, helping decrease the health risks placed on the public.

5: You Don’t Have to Fill Up the DEF with Each Tank

Diesel exhaust fluid is used at a rate of about 3% – 5% of fuel consumption so you will not need to replace the DEF every time you fill up the tank.

6: DEF Can Improve Fuel Mileage

There is a misconception that DEF is going to reduce fuel economy, but the truth is that many manufacturers and end-users alike have discovered that DEF actually provides better fuel economy for fleets.

7: DEF Has Been Used for Decades

While it is relatively new to the transportation industry in the U.S., SCR and DEF technology has been used for decades in many commercial and agricultural applications throughout Europe. It’s important that you only use environmental grade DEF for your SCR system, though, since urea designed for other uses could degrade your system.

Certified DEF is the premier source for high quality diesel exhaust fluid, and the place where you can get the products you need at a great price.  Contact Us for pricing or additional information.

How to Unlock the Potential of DEF Every Time

Diesel exhaust fluid (DEF) is new to the market, having only just been mandated in 2010 for Heavy Duty trucks. Drivers and fleet managers need to be aware of its sensitivities to contamination and the subsequent effects on its performance if contamination occurs.

We can help customers on the proper way of filling their tanks if they ask for that information. But, we thought, why wait for them to ask when we can post that information on our blog? So we compiled some of the best practices drivers can adopt to ensure the purity of their DEF, and put them here.

Better Out of the Way

The first thing that needs to remembered is that DEF is incredibly sensitive and needs to be free of contaminants, otherwise you run the risk of system failure which is extremely expensive and time consuming. DEF dedicated equipment should be used at all times when handling the fluid to ensure a properly functioning Selective Catalytic System (SCR) and should always be stowed in a contaminate-free environment when not in use.

Compulsion Against Contaminates

The dispensing nozzles and the dust caps need to be free of dust or small debris whenever in use. The former needs to be in its holding holster when it’s not in use to prevent any kind of spills or mishandling.

Only use DEF that is sealed upon arrival and never store DEF in a container that has been used to dispense other fluids without a proper washout. If dispensing from a tote, we highly recommend either discontinuing use after the product is empty or sending it back to your supplier for a thorough washout before dispensing DEF again. Some suppliers offer to refill totes as long as the seal hasn’t been broken, which is also a safe and reliable option. We do not, however, recommend reusing drums to dispense DEF since there’s no way to seal the container.

The gist of this entire post is that cleanliness is next to optimum DEF performance. Vigilance in ensuring that everything is free of contaminants is the key to maintaining the purity and quality of your DEF, which in turn ensures your engine performs at its highest level. But if you still have questions regarding the use of DEF, don’t hesitate to contact us immediately. You can also ask us about the other products and services we offer on the rest of our website.

The Importance of Maintaining DEF Purity

Diesel exhaust fluid (DEF) has been in truckers’ lexicon for close to a decade, and though there have been a few bumps in the road, the implementation of cleaner technology has been for the best.

Where It’s Been

Poor quality DEF or contaminants are the main reasons for the problems experienced with diesel exhaust fluid; problems that are easy to avoid as long as you get your DEF from reputable and reliable sources. There’s no need to test the purity of the product before they putting it in your engines, you can simply check if the outlet is registered with the American Petroleum Institute (API), which a company can easily prove with a certificate.

Some individuals try to save by using non-registered outlets, but that strategy can severely backfire if you’re not careful. If impure or contaminated DEF manages to find its way into an engine, it could cause the catalyst to fail and incur hefty damages, costing thousands of dollars. If that price tag isn’t enough reason to ensure that you only use DEF that is certified as pure, there probably isn’t a good enough reason.

What’s Coming

The job of keeping DEF pure doesn’t end once the container is on hand, though; there are still plenty of tasks needed to maintain its quality. Any kind of natural element, such as water, dirt, oil, dust, grease, fuel, metal fillings, and even detergent, can be bad news for DEF. It’s important to store in a clean environment, with the seals and lids still intact and only using the DEF dedicated container that it arrived in.

It’s also important to understand that this sensitivity to foreign elements can prove problematic when it comes to cleaning time. DEF dedicated containers will get dirty with time, which is bad for DEF. The solution is to use ONLY de-mineralized water when cleaning—no soap and no tap water—and dry everything off with a clean rag before refilling. However, it’s best to leave that to the professionals so you don’t run the risk of contamination.

It’s important to remember that DEF is a sensitive fluid that relies on a delicate balance to deliver clean performance. Fortunately, you can contact us for more information regarding DEF care, or explore the rest of our website for more information regarding locations and DEF solutions.