How to Make Your Own DEF Fluid: A Step-by-Step Guide

Have you been looking for a way to make your own DEF fluid? DEF stands for diesel exhaust fluid and is a solution used in diesel engines to reduce harmful emissions. This fluid is essential in keeping your diesel engine running smoothly while helping to save the environment. The good news is that you don’t have to rely on store-bought DEF fluids, and you can make your own at home with some simple ingredients.

Making your own DEF fluid is not only cost-effective, but it is also easy to do. The ingredients needed to make your own DEF fluid can be found at any hardware store or online. To make your own DEF fluid, you will need to mix water and urea in a specific ratio to create a solution that matches the specifications of the engine manufacturer. This process may sound complicated, but with the right guidance, anyone can make their own DEF fluid at home. Save time, money, and the environment by making your own DEF fluid today.

Understanding the Function of DEF Fluid

Before we dive into the topic of making your own DEF fluid, it’s important to understand exactly what DEF is and its function in a diesel engine. DEF stands for Diesel Exhaust Fluid. It’s a solution made up of pure, automotive-grade urea and deionized water. The purpose of DEF is to reduce harmful emissions that diesel engines produce. When DEF is injected into the engine’s exhaust stream, it breaks down hazardous nitrogen oxides (NOx) into harmless nitrogen and water vapor.

  • DEF is essential for meeting government standards. Several countries have implemented strict limits for diesel engine emissions, and DEF is one of the most effective solutions to meet these regulations.
  • DEF is not a fuel additive. It’s not used to improve fuel efficiency or engine performance. DEF must be used in a separate tank and is injected into the exhaust system after combustion takes place.
  • DEF must meet certain quality standards. The American Petroleum Institute (API) has established a set of quality standards for DEF. The API certification mark on a container of DEF indicates that it meets or exceeds these standards.

Overall, DEF is an integral component of modern diesel engines. It’s essential for meeting emission requirements and ensuring that diesel engines operate efficiently and sustainably. Now that you understand the function of DEF, let’s explore how to make your own DEF fluid.

The Importance of Using DEF Fluid

DEF or Diesel Exhaust Fluid is essential for the operation of modern diesel engines. It is a non-toxic, odorless, and colorless solution composed of 32.5% urea and 67.5% deionized water. DEF is added to the exhaust system of diesel engines to reduce harmful emissions and meet environmental regulations.

  • Environmentally friendly: DEF helps reduce harmful emissions of Nitrogen Oxides (NOx), which are a major contributor to air pollution. NOx is known to cause acid rain, smog, and respiratory problems in humans. By using DEF, diesel engines emit cleaner exhaust, making it environmentally friendly.
  • Cost-effective: Using DEF can improve fuel efficiency and prolong the life of your engine. DEF helps reduce the amount of fuel needed to run the engine, resulting in less frequent refueling. Additionally, DEF assists in cleaning the engine, reducing maintenance costs.
  • Mandatory in modern diesel engines: DEF is required by law in all modern diesel engines manufactured after 2010. The Environmental Protection Agency (EPA) and the Department of Transportation (DOT) strictly enforce this ruling. Failure to use DEF will result in hefty fines and could cause damage to your engine.

It is crucial to ensure that you use the correct DEF fluid for your engine. Each engine has its specific requirement for DEF, and using the wrong fluid could damage the engine. Always consult your engine manual or an expert before purchasing DEF.

DEF Fluid Properties Specification
Appearance Clear, colorless, and free of sediment
Urea Content 32.5%
Water Content 67.5%
Freezing Point -11°C / 12.2°F
Boiling Point 103°C / 217.4°F

Using DEF fluid is essential for the operation of modern diesel engines. It is environmentally friendly, cost-effective, and mandatory for compliance with the law. Always ensure that you use the correct DEF fluid and follow the proper handling procedures to ensure optimal engine performance.

Ingredients Required to Make DEF Fluid

DEF (Diesel Exhaust Fluid) is used in modern diesel vehicles with selective catalytic reduction technology to reduce harmful emissions. Here are the ingredients required to make DEF fluid:

  • Urea: This is the vital component in DEF, and it constitutes 32.5% of the fluid. Urea is an organic compound found in urine, horn, and other bodily fluids of animals and humans. It is processed through a synthetic process to form automotive-grade urea known as Diesel Exhaust Fluid (DEF).
  • Deionized Water: The remaining 67.5% of DEF fluid is composed of deionized water. The water should ideally be deionized and purified to eliminate any potential contaminants that can harm the SCR system of the diesel engine.
  • Additives: DEF suppliers may add additives to DEF to enhance its performance. For example, additives like stabilizers can prolong the shelf-life of DEF, making it less prone to bacteria growth, freeze prevention additives to ensure DEF doesn’t freeze during winter, and corrosion inhibitors to protect parts of the SCR system where DEF comes into contact.

How to Mix DEF Fluid Ingredients

Mixing DEF fluid ingredients is quite simple, and you can even make it at home. However, it is critical to ensure the measurements are accurate and that you are using the right equipment, so your homemade recipe doesn’t disrupt the SCR system’s performance. A small mistake in the proportioning of ingredients can result in engine damage and higher emission levels.

The most common way to mix ingredients is through batch blending. This involves measuring and loading the required urea and deionized water into a clean mixing tank. You can use a stainless or polypropylene tank to avoid contaminants that can affect DEF quality.

Components Volume size Percentage Ratio
Urea 32.5% 1:2.867
Deionized Water 67.5% 2.067:1

After loading the ingredients, agitate the mixture to ensure the urea dissolves in the water uniformly. You can use a pump or a paddle mixer to achieve an even blend of the ingredients. Measure the DEF’s density and urea concentration using a refractometer or hydrometer to ensure the concentration meets the ISO 22241 standard.

While it’s easy to make DEF fluid homemade, considering the critical role it plays in reducing vehicle emissions, it is advisable to buy DEF from a reputable supplier to ensure quality control and avoid making costly mistakes.

Step-by-Step Guide on Making DEF Fluid

DEF fluid is an essential component of the selective catalytic reduction system in diesel engines. It helps reduce nitrogen oxide emissions into the atmosphere by converting them into harmless nitrogen and water. While it can be readily purchased from most auto parts stores, making DEF fluid at home can be a cheaper alternative, especially if you have access to the right ingredients. Here are the steps on how to make DEF fluid:

  • Step 1: Gather the materials
  • Step 2: Measure and mix the ingredients
  • Step 3: Filter and store the DEF fluid

Let’s take a closer look at each step.

Step 1: Gather the materials

The first step in making DEF fluid is to gather the necessary materials. These include:

  • Purified water
  • Urea (Automotive Grade)
  • Measuring cup and spoon
  • Glass or plastic mixing container with a lid
  • Filter funnel and coffee filter, or a DEF filter
  • Storage container

Step 2: Measure and mix the ingredients

The second step is to measure and mix the ingredients in the mixing container. The recommended ratio is 32.5% urea and 67.5% purified water. Here’s how to mix them:

Ingredient Amount
Urea 32.5 grams or 1.12 ounces
Purified water 67.5 grams or 2.39 ounces

Measure the urea and water using the measuring cup and spoon. The urea may take some time to dissolve in the water, so stir the mixture until the urea is completely dissolved. Once the mixture is clear, cover it with the lid to avoid contamination.

Step 3: Filter and store the DEF fluid

The final step is to filter and store the DEF fluid. Filtering removes any impurities that may have been introduced during the mixing process. You can use a DEF filter or a filter funnel with a coffee filter to achieve this. Pour the mixture into the filter funnel or DEF filter and wait for it to pass through.

Once filtered, transfer the DEF fluid to a storage container and keep it in a cool and dry place until you’re ready to use it. Homemade DEF fluid has a shelf life of approximately six months.

In conclusion, making your DEF fluid is a simple process that can save you money in the long run. It requires minimal expertise and equipment, but you need to handle the materials with care and follow the instructions to the letter to avoid any mishaps. So, why not give it a try? You might just surprise yourself.

Quality Control Measures for Homemade DEF Fluid

One important aspect of making your own DEF fluid is ensuring that it meets the necessary standards to operate effectively in your diesel engine. Here are some quality control measures to consider:

  • Use high-quality ingredients: When making your own DEF fluid, make sure to use high-quality urea and deionized water to ensure the purity and consistency of the mixture.
  • Measure accurately: It’s essential to measure the ingredients accurately so the mixture meets the required concentration of 32.5% urea and 67.5% deionized water. A slight deviation from this ratio could negatively impact the performance of your engine.
  • Mix thoroughly: Proper mixing is crucial to ensure that the urea and deionized water are evenly distributed in the solution. Use a mixing system that agitates the mixture properly to achieve a homogenous mixture.

In addition to these measures, it’s also essential to test the quality of the DEF fluid you produce. Here are some tests to consider:

  • Freezing point test: DEF fluid will crystallize and become unusable if its freezing point is too high. Use a refractometer to measure the DEF’s freezing point to make sure it’s not above 12°F (-11°C).
  • Purity test: Use a test kit to measure the purity of your DEF fluid. The kit will show the levels of impurities such as calcium, sodium, and magnesium, which should be below 25 parts per million (ppm).
  • pH level test: DEF fluid with a pH level outside of the range of 9 to 11 is considered low quality and should not be used in your engine. Use a pH meter to test the pH level of your DEF fluid.


Making your own DEF fluid can save you money in the long run, but it’s essential to ensure that the quality of the fluid is not compromised. By using high-quality ingredients, measuring accurately, and testing the DEF fluid’s quality, you can produce a DEF fluid that meets the necessary standards and ensures the longevity of your diesel engine.

Quality Control Measure Why it’s important
Use high-quality ingredients To ensure the purity and consistency of the DEF fluid mixture.
Measure accurately To ensure the DEF fluid mixture meets the required 32.5% urea and 67.5% deionized water ratio.
Mix thoroughly To ensure that the DEF fluid is uniformly distributed.
Freezing point test To ensure that the DEF fluid will not crystallize and become unusable when the temperature dips too low.
Purity test To make sure the DEF fluid meets the required standards of less than 25 ppm impurities.
pH level test To ensure the DEF fluid’s pH level is within the accepted range of 9 to 11.

By following these quality control measures, you can produce a high-quality DEF fluid that will keep your diesel engine running smoothly for a long time to come.

Storage Techniques for Homemade DEF Fluid

Now that you’ve made your own DEF fluid, you need to store it properly to ensure it remains effective. Here are some tips for storing your homemade DEF fluid:

  • Store DEF fluid in a cool, dry place. Exposure to heat can cause the mixture to break down, and exposure to moisture can cause contamination.
  • Keep the DEF fluid in a sealed container. This will prevent moisture from getting in and keep the mixture fresh for longer.
  • Store the container upright. When DEF fluid is stored on its side, crystals can form and clog the system when the fluid is used later on.

DEF Fluid Storage Shelf Life

When stored properly, homemade DEF fluid can last up to one year. However, it’s important to regularly test the DEF fluid’s purity and acidity to ensure it remains effective. Here’s a breakdown of the shelf life of DEF fluid based on its storage temperature:

Storage Temperature Shelf Life
below 10°F (-12°C) 2 years
between 10°F and 90°F (-12°C and 32°C) 1 year
between 90°F and 100°F (32°C and 38°C) 6 months
above 100°F (38°C) 3 months

Using Homemade DEF Fluid

Before using your homemade DEF fluid, there are a few things to keep in mind:

  • Make sure the mixture is not contaminated. If there are any impurities, they can cause clogs in the system and reduce the effectiveness of the fluid.
  • Do not mix different batches of homemade DEF fluid. The different acidity levels can cause the mixture to break down and potentially damage your vehicle’s exhaust system.
  • Always follow the vehicle manufacturer’s guidelines for using DEF fluid. This will ensure your vehicle runs properly and meets emissions standards.

In Summary

When making and storing homemade DEF fluid, it’s important to take precautions to ensure the mixture remains effective. By storing DEF fluid in a cool, dry place and testing the purity and acidity regularly, you can extend the shelf life of your homemade mixture. Additionally, following your vehicle manufacturer’s guidelines for using DEF fluid will ensure your vehicle runs smoothly and meets emissions standards.

Compatibility of Homemade DEF Fluid with Diesel Engines

If you’re considering making your own DEF fluid, you may be wondering if it’s compatible with your diesel engine. DEF fluid is a critical component of diesel engines that helps reduce emissions, and using the wrong type of DEF fluid or one that isn’t compatible with your engine can cause serious problems, including engine damage and increased pollution.

  • Before making your own DEF fluid, it’s crucial to consult your engine’s manufacturer to see what specifications the DEF fluid needs to meet. DEF fluid typically needs to meet ISO 22241 standards, and any homemade DEF fluid should have the same properties as commercially available DEF fluid that meets these standards.
  • Keep in mind that homemade DEF fluid may not have consistent quality, which can lead to issues with your diesel engine’s SCR system, including clogged filters and reduced emissions control.
  • Additionally, homemade DEF fluid may not meet the same purity standards as commercially available DEF fluid, which can cause issues with DEF injectors and lead to increased engine wear over time.

It’s also important to note that using homemade DEF fluid may void your engine’s warranty, as many engine manufacturers require the use of only commercially available DEF fluid that meets their specifications.

Overall, while it may be possible to make your own DEF fluid, it’s important to weigh the potential risks and benefits before doing so. Consult your engine’s manufacturer to ensure that any homemade DEF fluid meets their specifications and won’t cause damage or void your warranty.

Compatibility Issues Potential Consequences
Using DEF fluid with incorrect properties or concentration Increased emissions, damage to SCR system components, engine damage and failure
Using DEF fluid that doesn’t meet ISO 22241 standards Lack of consistency in performance and quality, reduced emissions control, clogged DEF injector
Using homemade DEF fluid that doesn’t meet the same purity standards as commercially available DEF fluid Damage to DEF injectors, increased engine wear, reduced emissions control

It’s important to take these compatibility concerns into account if you decide to make your own DEF fluid.

Benefits of Making Your Own DEF Fluid

DEF fluid, or Diesel Exhaust Fluid, is a crucial component for modern diesel engines that helps reduce harmful emissions. While it is readily available at gas stations and other retailers, some individuals prefer to make their own DEF fluid. Here are some benefits of making your own DEF fluid:

  • Greater Control: By making your own DEF fluid, you have greater control over the quality and composition of the fluid. This can be especially important for those with specialized engines or those who operate in extreme conditions.
  • Cost Savings: Making your own DEF fluid can be significantly cheaper than buying pre-made fluid. The cost of the necessary ingredients is generally lower than the cost of pre-made fluid, and you can also save on transportation costs and other fees associated with retailers.
  • Reduced Waste: By making your own DEF fluid, you can reduce waste by only making what you need. This can be especially important for those who operate in remote areas or in areas with limited access to waste disposal facilities.

Ingredients Required to Make DEF Fluid

To make your own DEF fluid, you will need a few key ingredients:

  • Urea: Urea is the main ingredient in DEF fluid and is typically sold in granular or liquid form.
  • Deionized Water: Deionized water is used to dissolve the urea.

How to Make DEF Fluid

Now that you have the necessary ingredients, here are the steps to make your own DEF fluid:

  1. Measure out the correct amount of urea and deionized water based on the size of your DEF tank and the recommended ratio specified by your engine’s manufacturer.
  2. Add the urea to the deionized water and stir until it is completely dissolved.
  3. Pour the mixture into your engine’s DEF tank.
  4. Restart your engine and allow it to circulate the fluid throughout the system.
  5. Check the fluid levels and top off as necessary.


While making your own DEF fluid may not be for everyone, it can provide greater control, cost savings, and reduced waste for those who choose to do so. By following the above steps, you can easily make your own DEF fluid and maintain the efficiency and performance of your diesel engine.

Greater control over quality and composition May require additional time and effort
Cost savings Possible safety concerns when handling urea
Reduced waste May not be feasible for all engines or situations

Before making your own DEF fluid, be sure to consult your engine’s manufacturer and follow all safety guidelines to ensure proper handling and storage of the ingredients.

Cost Analysis of Making DEF Fluid vs. Buying DEF Fluid

Making your own DEF fluid may seem like a cost-efficient solution, especially if you have a fleet of vehicles that require it. However, before you decide to make your own DEF fluid, it’s essential to understand the cost breakdown and compare it to buying DEF fluid.

  • The cost of ingredients – Making your DEF fluid will require urea, and the cost of urea varies depending on several factors, such as location and supplier. On average, urea costs around $600 per metric ton, which translates to roughly $0.27 per pound. Apart from urea, you’ll also need to mix demineralized water, which is inexpensive, but the cost will vary depending on your location.
  • The cost of equipment – You’ll need a mixing tank to make your DEF fluid, and the cost will depend on the size of the tank and the quality. A high-quality tank with a capacity of 500 gallons could cost upwards of $2,000.
  • Labor cost – Making your DEF fluid requires labor, and you’ll need to factor in the cost of labor, especially when scaling up.

In contrast, buying DEF fluid from a supplier can cost anywhere from $1.50 to $2.50 per gallon. The cost of buying DEF fluid will vary depending on the supplier, location, and quantity ordered.

Based on a simple cost analysis, it’s clear that making your DEF fluid is not cost-efficient, especially when you factor in the cost of equipment and labor. Additionally, buying DEF fluid comes with the assurance of quality and compliance, which is essential in meeting regulatory standards.

Factors Making your own DEF fluid Buying DEF fluid
Cost of ingredients Varies, but on average around $0.27 per pound of urea Varies depending on the supplier, but on average $1.50 to $2.50 per gallon
Cost of equipment Varies depending on the size and quality of the mixing tank. A high-quality tank can cost upwards of $2,000 No equipment cost incurred
Labor cost Varies depending on the number of personnel required and the amount of DEF fluid produced No labor cost incurred

In summary, buying DEF fluid is cost-effective and assures compliance with regulatory standards. However, if you still choose to make your DEF fluid, ensure to weigh the costs and invest in high-quality equipment to guarantee quality.

Legal Implications of Making and Using Homemade DEF Fluid

Making your own Diesel Exhaust Fluid (DEF) at home can be an appealing option for some vehicle owners. However, it’s important to consider the legal implications of DIY DEF before taking matters into your own hands.

  • First and foremost, it’s essential to note that designing, manufacturing, and distributing any product that is intended to be used by vehicles on public roads is illegal. This means that even producing DEF for personal use could potentially cause legal issues.
  • If you’re caught using homemade DEF in your vehicle, you could face fines, penalties, or even legal action for violating the Clean Air Act. This act regulates emissions from vehicles and equipment, and using improper or non-compliant DEF can result in harmful emissions that pollute the air and threaten public health.
  • In addition, using homemade DEF could also compromise your vehicle’s warranty. Many manufacturers require that owners use only certified DEF products to ensure optimal performance and prevent damage to the engine or exhaust system. Using homemade DEF can void your warranty and leave you with costly repairs.

Overall, the legal implications of making and using homemade DEF are significant and should not be taken lightly. If you’re in doubt about the legality of a particular DIY DEF recipe or process, consult with a professional before proceeding.

It’s also worth noting that DEF is widely available and relatively affordable from reputable suppliers. While homemade DEF might seem like a cost-saving measure, the potential risks and legal ramifications are simply not worth it.

Legal Risks of Homemade DEF Consequences
Violation of Clean Air Act Fines, penalties, and/or legal action
Compromised Vehicle Warranty Costly repairs and voided warranty
Production/Distribution of Illegal Product Potential legal issues and fines

Ultimately, the safest and most legal option is to purchase certified DEF from reputable suppliers and ensure that it meets industry standards and regulations.

FAQs: How to Make Your Own DEF Fluid?

Q: What is DEF fluid?

DEF stands for Diesel Exhaust Fluid, which is a solution made of 67.5% water and 32.5% urea. It is used in diesel engines to reduce emissions and meet environmental regulations.

Q: Why would I need to make my own DEF fluid?

Making your own DEF fluid can be a cost-effective alternative to buying pre-made DEF from the store. It can also be useful in emergency situations when pre-made DEF is not available.

Q: What ingredients do I need to make DEF fluid?

To make DEF fluid, you will need high-quality urea powder, distilled or deionized water, and a measuring scale.

Q: How do I mix the ingredients to make DEF fluid?

Measure out the required amount of urea powder and slowly add it to the water while stirring continuously until it dissolves completely. The solution may heat up when mixing, so allow it to cool before using.

Q: How do I store DEF fluid that I made?

Store the homemade DEF fluid in a clean, sealed container and keep it protected from sunlight and extreme temperatures. It is essential to keep the mixture clean to avoid contamination that can damage your vehicle’s exhaust system.

Q: Can I use homemade DEF fluid in any diesel engine?

Yes, you can use homemade DEF fluid in any diesel engine that requires DEF fluid. However, always consult your manufacturer’s manual or experts before using homemade DEF fluid.

Q: Can homemade DEF fluid replace all commercially available DEF fluids?

Homemade DEF fluid can match the quality of commercial DEF fluids. However, the pre-made DEF fluids undergo rigorous quality testing to ensure that they meet OEM specifications. So, while making homemade DEF fluid can work as an alternative, it is essential to follow proper guidelines.

Closing Thoughts

Now that you know how to make your own DEF fluid, you can save money and be prepared in emergency situations. Remember, always follow the proper guidelines and consult your manufacturer’s manual or experts. Thanks for reading and visit us again for more insights.