Diesel Exhaust Fluid

Understanding Urea Injection





What is the purpose of Urea Injection?

Urea injection is part of the selective catalyst reduction (SCR) system. The purpose is to reduce emissions of nitrous oxides.


Does Urea have anything to do with Urine?

Urea is a component of diesel exhaust fluid (DEF is about 32% urea), and though it is also a substance found in urine they have nothing to do with one another. No, you can not urinate in your DEF tank. DEF is urea + water, and the percentages of each are vital to the reduction reaction that takes place when they are mixed into the exhaust stream.


How often will I have to fill my Urea Tank?

Ideally, your DEF tank should require filling at ever oil change interval. Heavy towing or a heavy right foot will use DEF at a faster pace, meaning the engine may require topping off between oil changes.


What happens if the DEF tank runs out?

If your DEF tank runs dry, the engine will automatically de-rate itself (lower performance) until the tank is refilled. To avoid running out, your tank should be filled at every oil change, and don't be afraid to top-off between oil changes as DEF usage increases with towing or other high-load operating conditions.


How big is the DEF tank on the 6.7L Power Stroke?

The reductant tank capacity on the 6.7L Power Stroke is approximately 5.2 gallons for inboard, frame mounted tanks and 5.73 gallons for outboard, frame mounted tanks.


How big is the DEF tank on the 6.6L Duramax LML?

The DEF tank on the 6.6L Duramax is approximately 5.2 gallons.


What happens if I spill DEF on my truck?

Urea is corrosive, so if you spill some on your truck you'll need to clean it up immediately to avoid the possibility of damaging your paint. Dilute it with soapy water, the corrosive properties of urea do not start stripping away paint immediately.


Why Doesn't the 6.7L Cummins Use DEF?

Cummins has opted out of using urea injection on their trucks for the time being. It remains a strong selling point, as keeping the DEF tank full presents an inconvenience to owners. Obviously, the Cummins meets emissions requirements without it. We predict that, in time, the 6.7L Cummins will turn to urea injection to reduce emissions and increase fuel economy. Their competitors have seen a 20% improvement in fuel economy on DPF equipped trucks.
















































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