Reducing NOx emissions is the aim of DEF, as they are a contributing factor to acid rain and smog. DEF decomposes into ammonia when it is introduced into the hot exhaust fumes. Ammonia then combines with the NOx to produce water vapor and harmless nitrogen gas. This chemical reaction, known as selective catalytic reduction (SCR), can eliminate over 90% of NOx emissions from the exhaust when the DEF system is operating properly.
All modern diesel vehicles with SCR systems rely on DEF to lower emissions to mandated levels. DEF actively cleans the exhaust rather than just filtering particles like a diesel particulate filter. Most diesel pickups, SUVs, cars, and commercial trucks today use DEF, so it has become a critical fluid for diesel engine operation and emissions compliance. In this blog post by Azure Chemical, we’ll analyze the expiry date of DEF and the factors included in its expiration.
Contents
Why Was DEF Introduced?
In order to help diesel engines comply with the stringent emissions rules implemented by the Environmental Protection Agency (EPA) in the United States, Diesel Exhaust Fluid (DEF) was invented.
Nearly all new diesel engines sold in the United States starting in 2010 are required to employ DEF in conjunction with an SCR system. Before being released from the exhaust, nitrogen oxide (NOx), an exhaust pollutant, is converted by DEF into nitrogen and water vapor, which are innocuous.
The EPA mandated the use of DEF and SCR technology to reduce NOx emissions from heavy-duty diesel vehicles like trucks and buses. Compared to previous emissions standards, the 2010 regulations enacted by the EPA reduced allowable NOx emissions by over 90%. Most older diesel vehicles could not meet these strict new standards without added emissions control systems like DEF.
By requiring new diesel engines to utilize DEF, the EPA significantly reduced the overall NOx pollution produced by diesel vehicles across the United States. DEF has become an essential component in meeting modern, clean air regulations.
How Long Does DEF Last?
Diesel Exhaust Fluid (DEF) has a shelf life of approximately 1-2 years when stored properly.
However, several factors can reduce how long DEF lasts:
Heat
Exposing DEF to high temperatures accelerates the rate at which the urea breaks down. Storing DEF in hot environments like a garage or shed can shorten its shelf life.
Microbial Growth
Bacteria and fungi present in DEF can multiply over time, accelerating the decomposition of urea. Keeping storage containers sealed helps prevent contamination.
Sunlight Exposure
Direct sunlight and UV rays hasten the breakdown of DEF—store containers out of direct sunlight.
The most obvious sign that DEF has expired is a change in its appearance. Fresh DEF is a clear, colorless liquid. As DEF ages and decomposes, it turns increasingly cloudy. A yellow or brown color indicates the area has started to break down and DEF is past its usable life.
While DEF can technically last 1-2 years in ideal storage conditions, heat, sunlight, and microbial growth often reduce shelf life to 6-12 months. Check DEF regularly for any color change to avoid using degraded fluid. Replacing outdated DEF helps prevent deposit buildups and maintains your vehicle’s SCR system.
Signs that DEF Has Expired
Diesel Exhaust Fluid can show some clear signs when it has expired and degraded in quality.
Here are the main things to look out for:
Change to Milky or Yellow Color
Fresh DEF is clear and colorless. If your DEF has turned cloudy, milk-like, or yellowish, that is a sign it has been contaminated and expired. The area has likely broken down.
Crystallization
DEF tends to crystallize as it ages and degrades. You may see solid crystals or chunky sediment forming in old, expired DEF.
Higher Viscosity
DEF in good condition should flow smoothly. Increased thickness or viscosity is a sign of contamination and expiration. The fluid may become sticky or syrupy.
Checking the appearance, texture, and flow of your Diesel Exhaust Fluid can provide good clues on whether it has gone bad. If you notice any of those three main symptoms, it’s time to drain the tank and replace your DEF supply. Expired DEF can cause deposits and clogs in your selective catalytic reduction system.
Should I Use Expired DEF?
Using expired DEF is not recommended and can lead to serious issues with your vehicle’s emissions control system. The urea solution in DEF breaks down over time, particularly when improperly stored at high temperatures. As DEF ages past its expiration date, the urea decomposes into ammonia. This affects the solution’s performance in the selective catalytic reduction (SCR) system.
Injecting aged DEF can corrode and clog vital engine components like the DEF injector, sensors, and catalytic converter. It may not allow your SCR system to function properly, leading to higher NOx emissions. Using expired DEF can also trigger diagnostic trouble codes and warning lights due to incorrect dosing or sensor readings.
The decomposition process also forms crystals that can damage injectors and clog filters, keeping contaminants from the DEF tank. Hardened deposits throughout the SCR system can lead to blockages, leaks, and costly repairs.
To avoid complications, it’s important always to use fresh DEF within the expiration date. Check the expiration date on DEF containers before refilling your tank. Properly storing and handling DEF will help prolong its usable life. However, to maintain emissions compliance and engine performance, expired DEF should not be used in any circumstances.
How to Store DEF Correctly
Maintaining the efficacy and quality of diesel exhaust fluid (DEF) requires proper storage. Here are some key storage tips to keep DEF in ideal condition:
- Keep DEF in the original sealed container. Opening the container exposes the fluid to contaminants and moisture in the air, which can degrade the DEF over time.
- DEF canisters should be kept in a cool, dry area away from direct sunlight. DEF can break down more quickly in the sun and at hot temperatures; store it between 23°F and 77°F.
- Avoid freezing and thawing. Freezing DEF damages the fluid over multiple freeze-thaw cycles. If DEF freezes, allow it to thaw and return to a liquid state before using it fully.
- Prevent exposure to extremely high temperatures. While DEF can withstand high heat in the vehicle’s hot exhaust system, prolonged exposure to temperatures over 86°F in storage will degrade DEF over time.
- Keep away from direct contact with moisture. Humidity causes DEF to degrade more rapidly. If possible, store indoors in a dry place.
- Check containers regularly for signs of crystallization or contamination. Crystals forming around the cap or nozzle may indicate DEF has been compromised. Discard if contamination is suspected.
Properly storing DEF helps maintain its effectiveness in reducing NOx emissions. Following these simple guidelines will help prevent premature degradation and extend the usable life of your diesel exhaust fluid.
How to Dispose of Old DEF
Diesel exhaust fluid (DEF) contains urea, which can harm the environment if disposed improperly. Here are some key guidelines for DEF disposal:
- Do not pour DEF down a drain or into the ground. The high nitrogen content of urea can contaminate groundwater and stimulate algae growth.
- Avoid disposing of DEF in the trash. The bottles and jugs can leak urea into landfills.
- Check your state and local guidelines for proper urea disposal. Some states prohibit disposal in landfills and sewer systems. Auto parts stores may accept old DEF for recycling.
- If old DEF has not degraded in quality, use it in your vehicle. Expired but still viable DEF is better than waste.
- Contact local hazardous waste management authorities to find authorized disposal sites for automotive fluids. Some collection events accept old DEF.
- Ask your diesel vehicle dealer if they can properly take back and dispose of outdated DEF. Dealers often have disposal programs in place.
- A professional hazardous waste handler can process and safely dispose of old DEF for large volumes.
Proper DEF disposal protects the environment and water quality. Old diesel exhaust fluid can be disposed of correctly with some care. Check local guidelines and use recommended disposal sites when possible.
When to Replace/Refill DEF
Diesel exhaust fluid (DEF) levels should be monitored regularly. DEF tanks are typically sized to go at least 5,000 miles between refills, but this can vary depending on your driving and engine conditions. It’s important not to let your DEF tank run empty, as this may cause your engine to derate or not start.
Plan to refill your DEF tank whenever it gets low, usually when the level falls below 1/4 tank. Most diesel engines have a DEF gauge, warning lights, or other alerts to tell you when the tank needs refilling.
In addition to refilling when low, DEF should be replaced at least once per year, regardless of mileage. This helps maintain the fluid’s quality and effectiveness. Over time, DEF can degrade due to heat cycles, exposure to contaminants, and normal aging, even if stored properly.
Replacing your DEF annually is good preventive maintenance for your diesel engine. Always use new, high-quality DEF that meets ISO 22241 specifications when refilling. Avoid “topping off” the tank; only add the necessary amount of fluid. Properly stored and replaced, DEF will help keep your emissions control system functioning for miles.
DEF Quality Standards
Diesel Exhaust Fluid (DEF) that meets ISO 22241 standards and has API certification ensures high quality and reliable performance. DEF fluid must adhere to rigorous specifications to receive API certification and meet OEM requirements.
The International Organization for Standardization (ISO) 22241 standard specifies critical quality criteria for DEF:
Purity
DEF must have a 31.8% and 33.2% urea content to avoid deposits or corrosion.
Alkalinity
pH level must be between 8.0 and 10.0.
Biuret
Biuret levels, a urea derivative, must be below 0.3% to avoid the formation of solids.
Aldehydes
Aldehydes must not exceed 20 ppm to prevent injection system damage.
Insoluble Matter
Insolubles must be below 80 ppm to avoid deposits.
Phosphates
Phosphate content must be below 0.5 ppm to avoid poisoning catalytic converters.
The ISO 22241 requirements ensure that DEF has the right composition to convert NOx emissions properly without causing buildup or damage.
Through a licensing program, the American Petroleum Institute (API) also certifies DEF products that satisfy ISO 22241 and additional automaker specifications. API certification helps guarantee DEF quality for diesel vehicle exhaust after-treatment systems.
You can rely on excellent performance and protect your vehicle’s emissions system using only API-certified DEF fluid that meets the latest ISO 22241 standards. High-standard DEF poses no threat of mechanical problems, deposits, or unexpected failures.
Frequently Asked Questions
You asked, we answered.
Does Diesel Exhaust Fluid (DEF) Have An Expiry Date?
Yes, DEF does have an expiry date. Generally, DEF has a shelf life of two years if stored correctly. However, this period can be shorter if exposed to direct sunlight or kept in hot temperatures for an extended period.
What Happens If I Use Expired DEF?
Ideally, you shouldn’t use expired DEF as it gradually loses its effectiveness over time, affecting your vehicle’s emissions performance. Your vehicle’s DEF sensor may detect the expired solution and trigger a fault code.
How Can I Determine The Expiry of DEF?
Most DEF manufacturers print the manufacturer’s date on the packaging. You can usually calculate the expiration date from this information. However, remember that real lifespan depends significantly on storage conditions.
Does Stored DEF Require Specific Conditions To Prolong Its Shelf Life?
Yes, to extend DEF’s shelf life, it should be stored in a cool, dry, well-ventilated area, out of direct sunlight. Optimal storage temperatures for DEF are between 15°F and 77°F (-10°C and 25°C).
Key Takeaways
Diesel exhaust fluid (DEF) is essential for reducing emissions in diesel vehicles with selective catalytic reduction systems. While DEF has an expected shelf life of 12 months, it can degrade in quality after six months if not stored properly. Here are the key takeaways:
- DEF is susceptible to degradation from heat and contamination. Store DEF in a cool, dry place between 12°F – 86°F.
- Check the DEF gauge regularly and refill the tank when it gets low. Running out of DEF can cause engine problems.
- Replace DEF every 12 months or after 10,000-15,000 miles to maintain optimal performance. DEF has a limited shelf life.
- Do not use contaminated, frozen, or expired DEF in your vehicle. This can damage the SCR system.
- Dispose of old DEF properly. Do not pour it down the drain. Check local regulations for hazardous waste disposal.
- Maintain the DEF tank per the manufacturer’s instructions to prevent buildup and corrosion.
Regularly replacing DEF is crucial for emissions compliance and engine performance. Always use fresh, high-quality Azure DEF within the vehicle’s recommended shelf life. Expired fluid can ultimately do more harm than good. Get in touch with us to schedule your delivery!
