Best DEF Refractometer In 2022: Test DEF Easily


Their foul odors, billowing smoke, and clatter could quickly identify older diesel engines. Modern technology has eliminated most of the unpleasant side effects of diesel engines. DEF is one way to do this. DEF is a fluid injected into your vehicle’s emission system to reduce pollution from diesel engines.

Standard DEF should contain an aqueous solution of 32.5% urea with 67.5% deionized waters. However, not all brands adhere to this requirement. To test the quality of DEF, we use DEF refractometers.

The process of injecting DEF into nitrous oxide emissions is known as Selective Catalytic Reduction or SCR. Advanced injection systems spray diesel exhaust pipes with DEF solution to significantly improve emissions. PACCAR, Detroit Diesel, and Cummins have incorporated SCR technology in their engine designs.

What is a DEF refractometer?

SCR-equipped diesel engines require that DEF be added to the machine periodically. SCR-equipped engines can only function well if DEF has a precise 32.5% urea concentration and 67.5% deionized waters concentration. A DEF Refractometer is used to measure engagement.

Test DEF using a Refractometer

It is easy to measure the UREA content in DEF material. A DEF Refractometer Kit is available for most diesel truck drivers, truck stop operators, and dealer service department personnel. The Refractometer portable is an optical device that can measure the DEF, a step-by-step procedure for testing a DEF using a refractometer.

Properly Adjust the Prism: Point the prism in bright light and examine the eyepiece.

Adjust the Diopter: Adjust your diopter until you can see the scale.

Zero Refractometer: Before you test DEF material, it is necessary to zero the refractometer. This calibration must be done before each DEF test to ensure the reliability of the results.

Clean the Device: Use clean water at the same temperature as the ambient and the provided cloth to clean any fingerprints.

Use water: Add two drops of distilled to the prism. To prevent water from running off, use the tool level.

Adjust waterline: Using a small screwdriver, adjust the shadow line to match the waterline to create a reference point to purify water.

Add DEF to The Prism: Use two drops of DEF on the prism and evenly distribute them on the prism’s surface.

Close it: Pull the cover tight.

Record Readings Take special note of where shadow meets percentage scale. This reading is essential.

Clean the Prism: Use an old cloth to clean the prism without immersing the whole instrument in water.

Before refilling, operators need to drain the DEF tank and flush it with distilled water. For convenience, DEF companies provide the solution in pre-mixed bottles or containers as a way for professionals to determine the DEF concentration by using visual and olfactory tests. You can use AdBlue or DEFBlue if you require a reliable DEF solution.

DEF is safe and non-toxic that is safe to use and poses no dangers to the health. Diesel operators need to store DEF safely, or they risk contamination.

How to read the DEF Refractometer

Place a drop of DEF on the instrument’s lens. The material is transparent, and the more concentrated the DEF solution is, the more light will bend. The refractometer has a graduated scale that ranges from 15% to 40%, with increments of 0.5%. A shadow appears on the scale when light passes through the prism.

How to read the DEF Refractometer

The shadow’s bottom edge touching the scale determines the concentration of DEF, indicating the 32.5% concentration at the bottom of the shadow.

The price range for DEF refractometers is from a few dollars up to a few hundred. Some devices can be used as a single device, while others measure only DEF concentrations. Amazon offers a good selection of DEF refractometers for comparing quality and value.

Top DEF Refractometers: The Best Choices

Low-sulfur fuel eliminates the smell. The timing of the fuel ignition improves to reduce diesel clatter. Everybody remembers the smell of black smoke coming from big rig trucks.

1. SE DEF Refractometer

This refractometer provides high-quality instrumentation across a wide range of scientific measurements. The DEF Refactor’s price is affordable without compromising quality.

The portable DEF Refractometer is applicable in a variety of ways. It is rugged and accurate and only requires a few drops to provide good readings. Automatic Temperature Compensation is an essential feature of the DEF Refractometer. This equipment comes with a 12-month warranty and 24-hour support.


  • Good quality and excellent price
  • Only 6.4 ounces in weigh


  • Calibration can prove difficult

2. OTC 5025 DEF Refractometer

Since 1925, Owatonna Tool Company has designed and built automotive test equipment. There are many specialty and diagnostic tools available at the company. The OTC 5025 compact unit features precision optics and is lightweight.

Refractometers have a graduation increase of 0.5 percent. Precision scales from 15 to 40 percent waterline and 20 degrees Celsius, and the product has 49 reviews, 92% of which are positive.


  • The tool is reliable and accurate, according to reviewers.
  • It is easy to read.


  • Some parts may be missing.
  • If you want to read, the dropper must have an extension.

3. Digital DEF Refractometer for Digital Laptops


The digital refractometer produces accurate results in a short time. You can place the DEF on the testing pad, and the results will appear in two seconds. You can test multiple times without any deterioration of results.

A 12-month warranty on the Digital Laptops Refractometer is a subscription to is included in the price, archiving the industry’s most extensive commercial fault codes. You can search for your fault code and view the results to clear it. You can also download the mobile app from this site.


  • Excellent result
  • The company offers a complete line of diagnostic tools
  • Clean, durable results


Owner/operators may not afford the price, but dealers and truck stops can.

Why Are DEF And Measuring DEF In Emissions Important?

Modern diesel technology had to be improved. A series of mandates from the EPA came into force in 2010. Diesel engine manufacturers were required to significantly reduce particulate matter (soot, ash) and toxic oxide emissions.

What is DEF and How to Measure DEF in Emissions?

The EPA dramatically increased diesel engine emission standards significantly, rolling out the diesel engine standards by 2010. New regulations also applied to diesel fuel. For example, it reduces the sulfur content of on-highway diesel fuel from 500 to 15 parts per million to 15.

Modern diesel engines burn a lighter mixture of fuel, meaning that the mixture contains less diesel fuel and more air. This combination is excellent for engine efficiency, but it’s not good for the environment. This process results in the production of more nitrous oxide.

Diesel engine manufacturers have few options without DEF too to meet the EPA standards. Volkswagen is a great reference of a manufacturer that has failed to succeed.

DEF is a fluid that contains urea and deionized waters. Urea is an organic compound made by combining nitrogen and hydrogen with carbon and oxygen. DEF is responsible for the breakdown of toxic nitrous oxide exhaust fumes. This chemical reaction produces the bi-products ammonia and carbon dioxide gas. These two gases react with nitrous oxide to form nitrogen and water, then exit the tailpipe.

The Key Takeaways

Anyone involved in diesel engine technology has greatly benefited from the DEF refractometer. This instrument makes it easier for dealers and service writers who are not qualified to fix problems they do not have to. A refractometer should be kept in the toolbox of all diesel truck operators to prevent the occurrence of many issues with diesel engines. This tool will eliminate any DEF problems.

The American ingenuity is evident in the DEF and SCR systems. Naysayers predicted that diesel engines would soon disappear when the EPA regulated heavy trucking emissions.

Nearly 81% of freight moves in the United States use trucks and diesel engines. Thanks to DEF and DEF Refractometer technologies, modern diesel engines are more efficient and energy-efficient.


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