DEF is a meticulously formulated blend of deionized water and urea. Hazardous nitrogen oxide (NOx) emissions are broken down into nitrogen and water vapor by DEF when it is introduced into the exhaust stream. This process makes the exhaust much cleaner, meeting emissions standards for diesel engines.
DEF was introduced in the early 2010s as diesel emission regulations became more stringent. All modern diesel vehicles with selective catalytic reduction (SCR) systems require DEF to reduce NOx emissions. DEF tanks need to be periodically refilled, usually at oil change intervals.
Using DEF is crucial for diesel engines to run cleanly. With it, vehicles will go into limp mode, have reduced power, and may even start. DEF helps today’s diesel cars, trucks, buses, heavy equipment, and more meet emissions requirements. Let’s learn all about the effects of putting DEF in diesel tank in this blog post by Azure Chemical.
Contents
- 1 Why DEF is Added to Diesel
- 2 Dangers of Putting DEF in Diesel Tank
- 3 DEF Concentration Matters
- 4 Engine Problems Caused by DEF in Diesel Tank
- 5 Fuel Filter Clogging
- 6 Breakdowns and No Starts
- 7 Fixing the Issue
- 8 Preventing DEF Contamination
- 9 The Cost of Repairs
- 10 Frequently Asked Questions
- 11 In Conclusion
Why DEF is Added to Diesel
Diesel Exhaust Fluid (DEF) is added to diesel to help convert nitrogen oxide (NOx) emissions into nitrogen and water.
This helps diesel engines meet the strict emissions standards of the Environmental Protection Agency (EPA).
Urea and deionized water combine to form the liquid solution known as DEF. Injecting it into the exhaust stream causes NOx to be broken down into innocuous nitrogen gas and water vapor. Byproducts of this chemical process can cut NOx emissions that cause smog by 90%.
All modern diesel engines are equipped with selective catalytic reduction (SCR) systems that utilize DEF. To comply with EPA emissions regulations, SCR technology is necessary for diesel cars, trucks, buses, heavy equipment, generators, and other machines. DEF effectively reduces air pollution from diesel exhaust.
Without DEF, diesel engines would emit unacceptable levels of NOx. That’s why DEF systems are standard on any new diesel vehicle or engine sold in the US. Maintaining the DEF system and filling the tank is crucial for proper emissions control.
Dangers of Putting DEF in Diesel Tank
Putting DEF in diesel tank can lead to serious problems with your engine and fuel system. DEF (Diesel Exhaust Fluid) is meant to be injected into the exhaust stream to lower NOx emissions. It is not formulated to be used as an engine fuel.
Adding DEF to your diesel tank will dilute the fuel and cause several issues:
Engine Damage
DEF can corrode metal engine components that are not designed to handle it. It also does not combust as efficiently as diesel, leading to combustion issues.
Clogged Fuel Filters
The urea crystals in DEF can clog fuel filters not designed to filter it, restricting fuel flow to the engine.
Vehicle Breakdowns
With contaminated fuel, engines can stall or not start. The vehicle can be left stranded until the DEF is drained from the tank.
Other Fuel System Problems
DEF residues can also clog fuel injectors and other components, leading to additional performance issues.
The bottom line is that you should never put DEF into a diesel fuel tank. It is incompatible with diesel engines and will cause performance problems and expensive repairs. Only refill the DEF tank with the new DEF. Ensure that the fill necks for the separate tanks are marked to avoid accidental contamination.
DEF Concentration Matters
While small amounts of DEF accidentally mixed with diesel fuel may not cause major issues, higher concentrations of DEF can lead to significant problems.
This is because DEF is composed of urea and deionized water. When DEF gets mixed into diesel at low concentrations like 5-10%, the diesel fuel can still normally combust. However, the DEF substantially dilutes the diesel fuel at higher concentrations, like 20% or more.
With the diesel diluted so much, it may not combust properly. The engine will run lean, meaning the mixture has more air than fuel. This lean condition can lead to a loss of power, misfires, stalling, and trouble starting the engine. Diluted fuel may also damage components of the fuel system that are not designed to handle urea. Overall, the higher the concentration of DEF mixed in, the more likely major issues will occur. A few ounces of DEF won’t hurt anything, but a few gallons mixed into a full diesel tank can spell trouble.
Engine Problems Caused by DEF in Diesel Tank
Adding DEF to a diesel fuel tank, even in small amounts, can seriously damage the fuel system components. DEF is corrosive to metals and will interact negatively with the materials used in diesel engine fuel systems.
One major issue is that DEF can corrode and damage vital fuel injectors. Fuel injectors are precision machined parts that must operate within very fine tolerances to atomize and inject the fuel properly. Corrosion from DEF contamination will degrade the injector tips and internal passages, leading to poor fuel atomization, decreased performance, and eventual injector failure.
DEF can also damage fuel pumps, particularly the precision high-pressure pumps used in modern common rail diesel injection systems. The corrosive DEF residues will score and ruin the finely machined surfaces inside the fuel pump, causing decreased fuel pressure, injection issues, and eventual pump seizure.
Sensors are another problematic area, as DEF residues corrode sensor tips and electrical contacts. This leads to all sorts of issues, including erroneous readings, check engine lights, incorrect fueling, and problems starting the engine.
Even small DEF in a diesel fuel tank can lead to corroded injectors, fuel pumps, sensors, and other vital components. This causes driveability issues, decreased performance, difficulty starting the engine, and eventual breakdowns as the contaminated components fail.
Fuel Filter Clogging
The urea in DEF can crystalize and clog fuel filters. This crystallization happens when the urea-water solution comes into contact with components it wasn’t designed for.
The diesel fuel system uses different metals and materials from the DEF system. When DEF enters the fuel tank, the urea interacts with these components and forms crystals.
These urea crystals will quickly clog up the fuel filter, preventing diesel from flowing properly to the engine. The engine will stall due to a choked fuel supply, run rough, and lose power if the fuel filter becomes blocked. Until the tainted gasoline filter is replaced, the truck cannot be started or operated.
It can be difficult to replace a fuel filter that has become blocked with urea crystals. The crystals can be stubborn, and it isn’t easy to fully clean out the fuel system. Multiple filter changes may be required to remove all of the contamination. Any remaining crystals will continue clogging the new filter. A full flush of the fuel lines may be necessary for severe DEF contamination of the diesel tank.
Breakdowns and No Starts
Putting DEF in diesel tank can lead to serious issues with starting and running the vehicle. The diesel exhaust fluid is not meant to be combusted like fuel so it can gum up injectors, fuel pumps, and other vital components.
When DEF gets into the fuel system, it can prevent the engine from getting the clean diesel it needs to fire the cylinders and run. Contaminated diesel may not ignite properly, causing misfires, rough running, stalls, or no starts. The engine computer may detect issues and put the vehicle into a limp mode to protect the engine.
A significant amount of DEF can water down the fuel if it enters the tank. The diluted fuel blend’s lower energy density and combustibility could leave drivers stranded when the engine cuts out or fails to start.
Getting the DEF contamination flushed from the entire fuel system is critical to get the engine running properly again. In severe cases, injectors, pumps, and other parts may need cleaning or replacement if they have been damaged from running on contaminated fuel. Until the whole system is purged, DEF-polluted diesel may cause breakdowns.
Fixing the Issue
If DEF has contaminated your diesel tank, the situation needs prompt attention and thorough fixing to avoid lasting damage.
Here are the main steps:
- Drain the diesel tank completely. This removes the contaminated fuel so it does not reach the engine. Draining may require disconnecting fuel lines and removing the tank. Properly dispose of the contaminated diesel/DEF mix.
- Flush the entire fuel system. After draining the tank, run a diesel-compatible flushing agent through the fuel lines, rail, injectors, and filters. The flush helps dissolve and remove any remaining DEF residue. Follow flushing agent directions.
- Clean the injectors. The injectors can be removed and cleaned individually, and the fuel system can be flushed to ensure no DEF deposits remain. If DIY cleaning is not feasible, a professional mechanic may be required.
- Replace all fuel filters. The fuel filter closest to the tank likely took the most contamination and needs replacement. Change all other fuel filters since residual DEF could be lingering. Use brand-new filters.
- Refill with fresh, pure diesel. After everything is cleaned and replaced, refill the tank with high-quality diesel with no DEF contamination. Run the engine to circulate the fresh fuel. Check for leaks or issues.
- Consider adding a fuel additive. A diesel fuel additive can help clean any remaining residue and lubricate components. Follow product instructions.
The fuel system flush, injector cleaning, and filter replacement are critical steps to remove all traces of the DEF and prevent ongoing issues. Take care to flush the entire system thoroughly. Replacing all fuel filters gives added assurance. Fresh diesel can safely run through a restored fuel system with contaminated components fully cleaned or replaced.
Preventing DEF Contamination
Careful handling and labeling of DEF is crucial to avoiding accidental contamination of diesel tanks.
When DEF is transported or stored, use clearly labeled separate containers from any fuels. Designate specific DEF-only funnels, pumps, and other equipment to eliminate cross-contamination.
When filling the DEF tank, take care to avoid spills or overflows into the diesel fill pipe. Pay close attention during the filling process. Only use DEF-approved containers and pumps. Wipe up any minor spills immediately to prevent residues from reaching fuel areas.
Follow all recommended DEF filling procedures in the owner’s manual. Do not try to top off the tank or overfill. Leave adequate ullage space for expansion. Secure the DEF fill cap tightly when done. Perform routine inspections of the DEF tank and supply equipment. Check for leaks, damage, or other issues that could lead to DEF entering the diesel system. Address any problems proactively.
Proper diligence and preventative maintenance can avoid DEF contamination of diesel fuel. Careful handling and filling of DEF are the keys.
The Cost of Repairs
Putting DEF in a diesel tank can be an extremely costly mistake. Cleaning out a contaminated fuel tank and replacing damaged components is costly. Here are some estimated repair costs:
Fuel Tank Cleaning
$200 to $500. The fuel tank must be completely drained, flushed, and cleaned to remove all traces of DEF contamination. This requires dropping the tank and bringing it to a shop with specialized equipment. Labor costs add up quickly.
Fuel Filter Replacement
$50 to $150. The fuel filter will be clogged with DEF crystals, so it must be replaced. Shop labor fees apply.
Injector Replacement
$350 to $700 per injector. DEF can damage the diesel injectors and require a full replacement. A diesel truck may have 4 to 8 injectors.
High-pressure Fuel Pump Replacement
$800 to $1,500. DEF exposure can ruin the high-pressure fuel injection pump, which is a major engine component replacement.
Additional Sensors and Parts
$500 and up. Other sensors and engine components like the fuel rail and regulator may also be damaged and need replacement.
Towing Fees
$100+. If the vehicle breaks down, it will need to be towed to the shop for repairs.
Rental Car Fees
Vary. You may need to rent a replacement vehicle while yours is being repaired.
Labor Costs
$100 to $200 per hour. Skilled mechanic labor isn’t cheap, so expect high hourly rates.
Frequently Asked Questions
What Happens if DEF Is Accidentally Added to a Diesel Tank?
Accidentally putting DEF into a diesel tank can cause serious damage to the fuel system. DEF is corrosive to many metals and can lead to the contamination of the fuel system, potentially resulting in clogged fuel injectors, damaged fuel pumps, and other critical engine components.
What Immediate Actions Should Be Taken if DEF Is Put in a Diesel Tank?
If DEF is accidentally added to a diesel tank, it’s crucial to avoid starting the engine. Starting the engine can circulate the contaminated fuel throughout the system, increasing the risk of damage. The next step should be to drain the tank immediately and flush the fuel system to remove any traces of DEF.
Can a Vehicle’s Warranty Be Voided by Adding DEF to the Diesel Tank?
Yes, adding DEF to the diesel fuel tank and causing damage to the engine or fuel system may void the warranty for those parts. Most vehicle warranties exclude damages caused by the use of improper fluids, including the accidental use of DEF in a diesel tank.
What Are the Long-term Effects of DEF Contamination in Diesel Fuel?
The long-term effects of DEF contamination in diesel fuel can be extensive and costly. They may include accelerated wear and tear on the fuel system, reduced engine performance, and even complete engine failure. Repairing the damage can be expensive, as it often involves replacing multiple components of the fuel system.
In Conclusion
As you can see, putting DEF in diesel tank can easily result in $2,000 to $4,000 or more in repairs if critical components like injectors and pumps need replacement. Avoid making this mistake at all costs, as cleaning the tank and fixing engine damage is very costly. If you ever need high quality DEF for your vehicle, then Azure Chemical is your go-to destination. With over 20+ years our experts could also provide you with the complementary instructions on DEF usage as well. Contact us today to schedule your delivery!
