Since its inception in 2001, the Duramax engine has established itself as one of the most influential and reliable diesel engines on the market. It has a ton of torque and can handle just about any job.
Of course, one of the most significant drawbacks of large, powerful diesel engines is fuel economy. While many vehicles have made strides through the years regarding improving fuel efficiency, vehicles with Duramax engines can’t make those same claims.
However, for a large diesel engine vehicle equipped with Duramax diesel engine get reasonably decent fuel economy. While you aren’t expecting a Prius when you buy a Duramax diesel, you should know what you’re getting before diving right in.
Where You Can Find a Duramax Diesel Engine
While GM produces Duramax engines, they own a wide array of vehicle lines. In the United States, you’ll primarily see Duramax engines in Chevys and GMCs. If you head overseas, you’ll see the same engine in the GM owned Isuzu brand.
The Silverado, Colorado, Sierra, and Canyon are the most common vehicles to have Duramax diesel engines – but you’ll also find Duramax engines in Chevy Express vans and the GMC Savana. While you don’t expect to be hauling a ton of things with a van, having that extra power and reliability can never hurt – especially considering the insanely large size of those vans.
The Two Duramax Diesel Engines
In 2001 GM released their first Duramax diesel engine. With a few minor tweaks and upgrades, it’s the same 6.6-liter engine found in the GMC Sierra and Chevy Silverado today. It puts out 910-foot pounds of torque, making it one of the most powerful diesel engines on the market.
But in 2016, General Motors was looking for a Duramax diesel engine that they could put in their midsize trucks to leverage the brand. What they came up with is a significantly smaller Duramax diesel. It’s only a 2.8-liter engine that puts out 369-foot pounds of torque.
Even more abhorrent to Duramax diesel purists, it’s a turbocharged four-cylinder engine. While both engines bear the Duramax name, they are entirely different beasts. You can find the smaller Duramax engine in both the GMC Canyon and the Chevy Colorado.
A Brief History of the Duramax Diesel
In 1998 GM and Isuzu launched a joint project called DMAX. One short year later, GM bought a 49 percent ownership share of Isuzu, becoming the largest shareholders, and taking over the company.
Meanwhile, in a factory in Moraine, Ohio, production for a massive diesel engine barreled on. It took 3-years, but in 2001 both GMC and Chevy had the 6.6-liter Duramax diesel unveiled as their new motor.
The design they released in 2001 was used until 2004, after which they switched from the composite design cylinder head to one made of aluminum. They made several other changes, all of which added up to an additional 70 pounds of torque.
While GM and Isuzu made multiple small changes until 2007, it wasn’t until then that the engine received another significant overhaul in terms of power output. At that point, GM upgraded the engine to put out a whopping 660 pounds of torque.
In 2017 GM released the most powerful Duramax ever – which puts out 910 pounds of torque. Of course, in 2016, GM released the 4-cylinder 2.8-liter Duramax engine, but it’s an entirely separate line from the 6.6-liter engine.
Truthfully calling it a Duramax is a play on the marketing success that the larger engine has had. The engine is different in every way, and while GM makes the 6.8-liter engine in Moraine, Ohio, they make the 2.8-liter engine in Rayong, Thailand.
Branding the smaller engine with a Duramax label has riled Duramax purists for years, and it’s not hard to see why.
Fuel Economy of the 3 Most Common 6.6-Liter Duramax Diesel Trucks
With the two Duramax diesel engines being so drastically different, it doesn’t make much sense to compare them head to head. Directly below are the three most common vehicles equipped with the 6.6-liter Duramax diesel engine.
All fuel economy statistics are derived from Fuelly.com. They compile real-time data from real drivers, so you get an accurate representation of a vehicle’s fuel economy – instead of a bloated statistic from the manufacturer.
The fuel economy of the Chevy Silverado 2500 and the GMC Sierra 3500HD are similar, while the GMC Sierra 2500HD gets a slightly better efficiency.
Chevy Silverado 2500
Looking at the trend, the Chevy Silverado 2500 fuel economy hasn’t been getting better through the years – it’s been getting worse. While early versions of the engine were getting close to or even over 15 miles per gallon, newer models are lucky to be hitting 14 miles per gallon.
With few changes scheduled over the next few years, it’s hard to see this trend turning around any time soon.
| Year | Miles Per Gallon |
| 2021 | 13.1 MPG |
| 2020 | 13.1 MPG |
| 2019 | 14.5 MPG |
| 2018 | 13.8 MPG |
| 2017 | 14.3 MPG |
| 2016 | 14.3 MPG |
| 2015 | 14.2 MPG |
| 2014 | 14.3 MPG |
| 2013 | 14.9 MPG |
| 2012 | 13.3 MPG |
| 2011 | 13.7 MPG |
| 2010 | 14.7 MPG |
| 2009 | 13.4 MPG |
| 2008 | 14.5 MPG |
| 2007 | 14.6 MPG |
| 2006 | 14.3 MPG |
| 2005 | 13.9 MPG |
| 2004 | 14.3 MPG |
| 2003 | 14.9 MPG |
| 2002 | 15.0 MPG |
| 2001 | 15.4 MPG |
GMC Sierra 2500HD
If any of these vehicles have had a steady fuel economy rating, it’s the GMC Sierra 2500HD. From 2011 to 2015, it couldn’t bust through the 14 miles per gallon barrier, but recent years match the numbers from the early 2000s.
If you’re looking to purchase a GMC Sierra 2500HD, you can expect between 14.5 and 15 miles per gallon. This is the best fuel economy you’ll find in a vehicle equipped with the 6.6-liter Duramax diesel.
| Year | Miles Per Gallon |
| 2021 | 14.7 MPG |
| 2020 | 14.7 MPG |
| 2019 | 14.4 MPG |
| 2018 | 15.3 MPG |
| 2017 | 14.2 MPG |
| 2016 | 14.4 MPG |
| 2015 | 13.9 MPG |
| 2014 | 13.7 MPG |
| 2013 | 13.4 MPG |
| 2012 | 13.7 MPG |
| 2011 | 13.9 MPG |
| 2010 | 15.0 MPG |
| 2009 | 14.6 MPG |
| 2008 | 14.4 MPG |
| 2007 | 14.3 MPG |
| 2006 | 14.7 MPG |
| 2005 | 13.6 MPG |
| 2004 | 15.5 MPG |
| 2003 | 15.2 MPG |
| 2002 | 15.0 MPG |
| 2001 | 14.2 MPG |
GMC Sierra 3500HD
With a few periodic dips in fuel efficiency through the years, the GMC Sierra 3500HD has stayed steady with a fuel economy right around 13.5 miles per gallon. With the 3500HD having a slightly larger body than the 2500HD, it’s not surprising that the fuel economy takes a bit of a hit.
But if you’re looking for the bigger truck, the enormous 6.6-liter Duramax diesel is easily powerful enough to take you and whatever you’re hauling from point A to point B.
| Year | Miles Per Gallon |
| 2021 | 13.6 MPG |
| 2020 | 13.6 MPG |
| 2019 | 11.2 MPG |
| 2018 | 11.8 MPG |
| 2017 | 13.3 MPG |
| 2016 | 13.6 MPG |
| 2015 | 14.3 MPG |
| 2014 | 12.2 MPG |
| 2013 | 12.5 MPG |
| 2012 | 13.3 MPG |
| 2011 | 13.7 MPG |
| 2010 | 13.2 MPG |
| 2009 | 15.1 MPG |
| 2008 | 13.3 MPG |
| 2007 | 13.6 MPG |
Fuel Economy of the 3 Most Common 2.8-Liter Duramax Diesel Trucks
The baby Duramax shouldn’t have its fuel economy compared with its massive V8 cousin. With only four cylinders and almost 600 fewer pounds of torque, it’s no wonder that you need to make fewer stops at the gas station.
Just like all the statistics above, the following fuel economy statistics are derived from Fuelly.com. This gives us an accurate representation of what actual drivers are experiencing instead of bloated numbers from the manufacturer.
Chevrolet Colorado
Like the Chevy Silverado, the Chevy Colorado is experiencing diminishing returns when it comes to fuel economy. Every year since the Colorado incorporated the 2.8-liter Duramax diesel fuel efficiency numbers have declined.
| Year | Miles Per Gallon |
| 2021 | 20.4 MPG |
| 2020 | 20.4 MPG |
| 2019 | 22.3 MPG |
| 2018 | 22.7 MPG |
| 2017 | 23.6 MPG |
| 2016 | 23.8 MPG |
GMC Canyon
After 2019 GMC Canyon drivers have noted a significant drop in fuel efficiency. Before 2018 drivers were consistently averaging over 24 miles per gallon. Since then, drivers are lucky to be getting 23 miles per gallon. It’s not clear why fuel efficiency is declining, but you’d expect the numbers to be heading in the other direction.
| Year | Miles Per Gallon |
| 2021 | 23.0 MPG |
| 2020 | 22.9 MPG |
| 2019 | 23.0 MPG |
| 2018 | 24.8 MPG |
| 2017 | 24.4 MPG |
| 2016 | 24.0 MPG |
Summary
While you’re not going to be buying a Duramax diesel engine because it’s going to save you some money at the pumps, it’s good to know how much you’ll need to budget before buying a vehicle.
While Duramax diesel engines aren’t terrible on fuel for a large diesel truck, they’ll still cost you a mint and leave you at the pumps more often than not.
Furthermore, there’s a big difference between the 6.6-liter Duramax diesel and its smaller cousin, the 2.8-liter. While you’ll get far better fuel economy with the smaller engine, you’ll also get far less power.
Truthfully, if you’re looking for a large, powerful diesel engine, ditch the worry over fuel efficiency and focus on reliability and power. When you look at it that way, you can’t beat the 6.6-liter Duramax.
