What Year Did Duramax Start Using DEF, and Why?

The Environmental Pollution Agency (EPA) has been implementing measures to reduce environmental pollution caused by diesel trucks. In 2010, the agency made Diesel Exhaust Fluid (DEF) compulsory for all diesel trucks, and since then, it has become a required component in any new diesel truck sold in the United States. One of the leading manufacturers of diesel engines, Duramax, also uses DEF, but the fact is that What Year Did Duramax Start Using DEF after it became mandatory?

This article will explore why Duramax started using DEF and its impact on their engines’ performance. Specifically, we will focus on the year when Duramax began using DEF and how this technology has helped to enhance their trucks’ efficiency while reducing emissions.

What is DEF?

DEF, or Diesel Exhaust Fluid, is a liquid used in diesel engines to reduce 90% of the pollution emitted from the exhaust system of a diesel engine that can be harmful to the environment and human health. DEF comprises 32.5% urea and 67.5% deionized water, making it safe for handling and storing.

DEF works by injecting a small amount into the exhaust stream of diesel engines through a system called Selective Catalytic Reduction (SCR). When heated, DEF breaks down into ammonia which reacts with nitrogen oxides (NOx) in the engine exhaust to form harmless nitrogen gas and water vapor.

What Year Did Duramax Start Using DEF?

What Year Did Duramax Start Using DEF?

The Environmental Protection Agency (EPA) has taken steps to address this issue by making it compulsory to use Diesel Exhaust Fluid or DEF.

Duramax started using DEF in their engines in 2011 till date. The Duramax engine’s DEF system first appeared in 2010, along with the introduction of the LML model.  

This fluid is composed of urea and deionized water that is added to the exhaust system of a diesel engine. It helps convert harmful nitrogen oxides into harmless nitrogen gas, reducing the pollutants released into the atmosphere.

Contrary to popular belief, using DEF does not compromise the performance of a diesel vehicle; rather, it improves fuel mileage and horsepower while reducing carbon dioxide emissions.

How often do I Need to Add DEF to My Truck?

One feature that sets Duramax apart from other diesel engines is its DEF tank, which holds 5.3 gallons of Diesel Exhaust Fluid (DEF) at the back of the engine. DEF is an essential component for reducing harmful emissions and meeting federal regulations. The rate at which it evaporates depends on various factors such as temperature, driving conditions, and altitude.

A typical 2.5-gallon container of DEF can last up to 3,000 miles before needing a refill, while a larger 5-gallon container can last up to 6,000 miles.

Duramax trucks will give you a low DEF warning when the fluid level reaches 10%, giving you plenty of time to refill before running out completely.

Why has EPA Made DEF Compulsory?

DEF can reduce up to 90% of pollution emitted from a diesel engine. As the world faces severe air pollution and climate change, such a move by EPA is crucial in fighting against carbon emissions.

 DEF works by mixing with exhaust gases and breaking down harmful pollutants into harmless Nitrogen and water vapor through Selective Catalytic Reduction (SCR). This process reduces harmful emissions and improves fuel efficiency, leading to lower fuel consumption and increased durability and longevity of the Duramax Engine.

Pros and Cons of DEF Truck:

What Year Did Duramax Start Using DEF?


  • Increase fuel efficiency.
  • It Reduces 90% of the pollution.
  • Increased Duramax’s horsepower.
  • Produces harmless Nitrogen and water through the exhaust.
  • Optimized fewer engine parts wear.
  • Increase the longevity of the engine.
  • Quickly DEF tank filling.


  • The main issue with DEF systems is that they must be covered under warranty by any truck manufacturer. If a problem arises with the DEF system, the owner must pay for repairs and replacements out of their pocket.
  • Changing the DEF fluid every 6k miles costs around $80, which adds an extra burden on truck owners.
  • This is unacceptable as it puts an unfair financial strain on individuals who rely on their trucks for work or other purposes.

Should I Remove My DEF?

Removing DEF from your truck will directly violate EPA regulations, making your warranty claim void if you do so. The EPA requires all diesel engines manufactured after 2010 to have DEF for a good reason – it reduces NOx emissions by up to 90%. Therefore, removing DEF can seriously harm the environment and can lead to fines by traffic police.

Final Wording About What Year Did Duramax Start Using DEF:

DEF helps reduce harmful nitrogen oxide emissions and prolong the engine’s life. As we look towards a more environmentally conscious future, we expect further diesel engine technology advancements that prioritize performance and sustainability.


Can DEF help to get better fuel mileage in 6.6 Duramax?

The answer is yes! DEF can lead to better fuel economy in a 6.6 Duramax engine because it helps the SCR system work more efficiently, reducing harmful emissions and increasing engine performance. The SCR system injects DEF into the exhaust stream, which converts nitrogen oxides (NOx) into harmless water vapor and nitrogen gas. This process reduces exhaust emissions while improving overall fuel efficiency.

What is the primary difference between LMM and LML?

One of the most notable differences between the LMM and LML is DEF or Diesel Exhaust Fluid. The LML engine comes equipped with a DEF system, whereas the older LMM does not have one.

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