Who Makes The Duramax V8 Engine & What Kind Of Horsepower Does It Produce?

When you're in the market for a truck and pondering your options, there's one consideration that's generally going to be a higher priority than any other — power. Trucks are often among the heftiest vehicles you might get behind the wheel of, and they're typically built for longer journeys, carrying considerable weight, and doing so in a manner that isn't too fatiguing or uncomfortable for the occupants. A powerful engine, then, is imperative to a truck's performance. 2024's GMC Sierra HD, for instance, is capable of towing 22,500 pounds, and powering it to these numbers is the Duramax V-8, a turbo-diesel engine provided as an option for those who need a bit more from the model.

Diesel is a common choice for a truck's powertrain, sometimes offering more power than a petrol counterpart. Depending on the type of journey you're taking and how laden your vehicle might be, it can be the right choice for many a heavier-duty ride. Truckers are probably familiar with Duramax's series of V-8s, which have powered a range of diesel trucks like the Sierra. You may not, however, be so familiar with the formidable powertrains' origins or exactly what they're capable of.

In this piece, we'll discover who manufactures the Duramax V-8 and the horsepower ranges the engines have offered, as well as a bit more about the vehicle families that have used the range.

The story of the Duramax V-8 engine begins with automobile industry heavyweight General Motors. Alongside Isuzu Motors Ltd, GM created DMAX Ltd. This new company was formed in 1998 with the intent of producing diesel engines, the manufacture of which began two years later. The very first model was completed in July 2000, and Duramax engines soon proved to be popular. In a May 2007 GM press release celebrating that one million of the engines had been created, GM Powertrain Global Manufacturing vice president John Buttermore boasted that the range represented "the strongest and quietest diesel on the market, and we continue to sell every single Duramax we can build."

By 2017, the company had doubled the number of engines produced. At this stage, 17 years after production of Duramax engines began, the range had expanded considerably. The very first Duramax was a 32-valve 6.6 liter turbodiesel, the LB7, and it was cleverly engineered. While diesel engines are potentially more powerful than a gasoline equivalent, they are also generally larger and more heftier. To help circumvent this issue, DMAX created its debut Duramax from an alloy of iron with aluminum pistons and implemented strengthened cylinder bores. Through such innovations, the aim was to create an engine with the typical advantages of a diesel (also including its strength) without the potentially detrimental size.

All of this translated to an engine that had great power compared to its peers from its very first iteration.

Though the first Duramax's specs seem more than a little modest today, at 300 HP, it was quite a sophisticated model for its time, with common rail capabilities. Next to the engine it replaced, the 215 HP IDI 6.5L, it was clear that this new powertrain was a significant upgrade. It was considerably more powerful, too, offering 520 lb-ft of torque compared to its predecessor's 440 lb-ft.

Of course, GMC trucks utilized the original Duramax V-8, such as the short bed edition of the 2001 GMC Sierra 2500 HD Crew Cab. Chevrolet models fitted with it include the Kodiak, which had the original Duramax from 2003 (the third generation model then boosted slightly to 304 HP). The next year, an improved model of the Duramax arrived: the LLY.

The LLY featured a Variable-Vane Turbocharger and separate fuel injection, thereby introducing targeted improvements without completely transforming the successful LB7. By not departing too much, though, it also didn't represent an enormous step forward, offering 310 HP. In 2007, this model was followed by the Duramax LMM, another V-8. By this time, the Duramax family sported 365 HP, and it still had considerable advancements to make yet. When introducing the 2011 Sierra range, a GMC press release of the time noted "a more powerful 6.6L Duramax turbodiesel that delivers 397 horsepower (296 kW) at 3,000 rpm and 765 lb.-ft. of torque (1,037 Nm) at 1,600 rpm."

Engine technology has had to advance in more ways than one. It's not only about the raw specs alone because other very important values need to be taken into consideration, too — emissions. As the Duramax V-8 evolved, it tried to balance both of these factors. The 2011 6.6L Duramax, accordingly, offered a Piezo fuel system and the option to utilize B20 biodiesel, such options contributing to a comparative decrease of 63% or more in NOx pollutants.

Following these models, the L5P engine was added to the family. It was first utilized in 2017, a 6.6 liter powerhouse that produced 445 horsepower. Midway through the 2024 model year, the L5P mounted in the Duramax V-8's long-time partner, the Silverado 2500 HD, had reached torque of almost 1000 and horsepower of 470 (yet another turbocharger upgrade was pivotal in this improvement). In a June 2023 first test of the model and engine, Motor Trend noted that "despite tipping the scales at a staggering 8,269 pounds, the Silverado 2500HD rocketed from 0 to 60 mph in just 6.4 seconds," an impressive feat for such a formidable diesel vehicle.

The Duramax V-8 may not be the most powerful diesel V-8 family (Ford reported that its 2023 Super Duty could hit "best-in-class 500 horsepower and 1,200 lb.-ft. of torque"), but it remains a powerful competitor in the class that it always has been.