Diesel Exhaust Fluid and the 2011 Duramax Diesel


The enhanced, legendary Duramax 6.6L Turbo Diesel is the most powerful Duramax ever built – generating more horsepower and torque than ever before. This proven powerplant gets the job done while being friendlier to the environment.

The improved Duramax uses the latest emission control technology, reducing Nitrogen Oxide (NOx) emissions by a whopping 63% when compared to the 2010 model. GM engineers determined the best way to accomplish this remarkable reduction of diesel emissions was to employ a Selective Catalytic Reduction (SCR) system that uses Diesel Exhaust Fluid (DEF).

Selective Catalytic Reduction (SCR)

The SCR system is an after-treatment system, since it treats the vehicle’s exhaust after combustion. Here’s how it works:

  1. A fine mist of DEF is injected into the exhaust while the engine is running
  2. The heat from the exhaust converts DEF into ammonia
  3. When the ammonia, mixed with exhaust gases, reaches the SCR catalyst, the NOx emissions are broken down
  4. The Diesel Particulate Filter (DPF) then captures soot to incinerate it during regeneration cycles.
  5. Water vapor, nitrogen and reduced emissions exit the exhaust system.

What is DEF?

Diesel Exhaust Fluid is a non-flammable fluid comprised of 33% ammonia-based urea and 67% purified water. DEF is used with diesel engine exhaust systems to reduce the amount of emissions produced by turning Nitrogen Oxide (NOx) into nitrogen and water vapor. DEF technology has a proven track record since it has been used in Europe for years.

Driving Range Between DEF Tank Refills

The SCR system uses DEF at a rate of about 1 to 1.25% of the vehicles diesel fuel usage. A full tank of DEF provides a driving range of about 8,000 km. Since DEF is directly related to fuel consumption, range will vary depending on driving conditions

Refilling Your DEF Tank

DEF is stored in a 5.3 gallon (approx 20L) tank located under the passenger side of the cab. The DEF tank fill point is conveniently located under the hood, along with other fluids that require periodic maintenance. It’s easly identified with a blue cap. DO NOT OVER FILL THE DEF TANK

Storing DEF

DEF shelf life is typically at least one year, depending on the storage temperature. It is best stored out of direct sunlight at room temperature. Small DEF spills can be cleaned up by absorbing it with dry earth, sand, or other non-combustible material and scooping it into a container for disposal. While DEF is not listed as a hazardous waste by the federal government, please use proper disposabl methods. Do not empty into drains; dispose of this material and its container in accordance with all applicable local and national regulations.

Electronic Onboard Warning System

There is no guessing involved when it comes to maintaining a correct DEF level with this system. An electronica onboard warning system provides you with numerous warnings in the Driver Information Center to help you maintain adequate DEF levels, alert you if the DEF quality is poor or if there are concerns with the system. See your Duramax owner’s manual supplement for a complete description of the electronic onboard warning system and its warning messages.

Maintaining DEF Fluid Levels

The electronic onboard warning system will provide a message alerting the driver when the DEF level is around 1,500 km remaining range. Additional messages that must be acknowledged alert the driver at the 500 km, LOW, and 0 km fluid ranges as the DEF tank gadually empties. The fluid level in the DEF tank must be maintained for the vehicle to run correctly. If the DEF tank is allowed to run empty, the system will alert the driver. If fluid is not added at the next vehicle start, the vehicle speed will be limited to approx. 88 km/hr and ultimately to 7 km/hr in accordance with federal requirements.

Adding DEF to an Empty or Low Tank

Always add at least 4 L to release the vehicle from any speed limitation. Once the system is refilled, the system resets itself and a service visit is not required. It may take up to 30 secondsin park or several km of driving to update the DEF level warning.

Will DEF Freeze?

DEF freezes at approximately -11 degrees celsius, so the tank and DEF system are designed to freeze in cold climates. If DEF is frozen, the vehicle will still start as it always has. There is a second tank inside the DEF tank that is heated in 270-minute intervals while the engine is running, to ensure DEF fluid is thawed. This cycle was originally 90 minutes and that produced some of the freezing problems with trucks located in cold climates for extended periods of time, but the new program extends the cycle to 270-minutes to ensure enough DEF is circulated to keep the truck running at optimal standards. Residual heat from this internal tank helps to heat and thaw the remaining DEF in the larger tank. Do not overfill your DEF tank, as freezing will cause the fluid to expand and in turn could damage the tank.

If you have any other questions about the DEF system in the 2011 Duramax, feel free to drop us a line or visit our website at