Duramax Diesel Generations By Year: A Complete History

General Motors' Duramax engine is one of the most legendary diesel engines, next to Ford's Power Stroke and the Cummins diesel engines in trucks like the Dodge Ram. But while it may not have the history of either of those names — especially not Cummins, which built its first engine in 1919 — the Duramax had technology on its side, at least when the 6.6-liter LB7 debuted in 2001.

Born out of a collaboration between GM and Isuzu, the 2001 Duramax took the fight to the more established diesel names with new technology and innovations that gave the engine more power and quieter, almost gasoline engine-like, running. But that was merely the start for GM: Since 2001, the automaker has released a long line of iterations on the basic building blocks, ranging from minor updates to completely new redesigns. GM hasn't shown any signs of stopping, either: with an updated L5P and second-generation 3.0-liter Duramax leading the charge in heavy- and light-duty trucks, respectively, we expect GM to continue to be a force in the diesel landscape for many years.

And so, as we approach the 25th anniversary of what has become a stalwart of modern diesel engines, let's take a look back and run through all the generations of GM's Duramax.

The first fruit of GM and Isuzu's partnership was the 6.6-liter Duramax LB7 engine that debuted in 2001 in heavy-duty pickups like the Chevrolet Silverado 2500HD, offering a fresh new start after the company's mediocre late-1980s diesel engines. The LB7 was notable for being one of the first diesel pickup engines with aluminum cylinder heads and for its common-rail fuel injection. The latter wasn't a new technology, of course, having featured in some mid-1990s Japanese engines, but GM at the very least beat rivals Ford and Cummins to the introduction of that particular tech.

The LB7 was also more powerful than its contemporary rivals: the LB7 made 300 hp and 520 lb-ft of torque when it debuted in GM pickup trucks like the 2001 GMC Sierra HD. Ford's 7.3-liter Power Stroke made 250 hp and 505 lb-ft of torque in its most powerful configuration, and the LB7 also left Chrysler's 245-hp, 505-lb-ft 5.9-liter Cummins in the dust when it came to raw power output.

As with any first-generation product, the LB7 wasn't without issues. While many often rate the LB7's three-year run as some of the best years for the Duramax, the LB7 has one common and potentially troublesome issue: the fuel injectors. The common-rail system itself was fine, but the injectors themselves tended to fail after 100,000 miles, with replacements quite expensive and troublesome to replace. GM thankfully didn't let this drag on for too long, though, and introduced a replacement engine mid-way into the Duramax's third year.

GM debuted a revised engine, the LLY, mid-way through 2004 for the Chevy Silverado and GMC Sierra 2500HD/3500HD — thus the "2004.5" model year that diesel enthusiasts often use when referring to this short-lived revision of the Duramax. GM didn't change all that much for the LLY, with the main differences being new fuel injectors, an updated turbo, and a revised VIN, the latter being the quickest way to tell the two engines apart.

GM redesigned the engine's injectors for the Duramax LLY, which meant that owners and mechanics could now service them externally. This eliminated much of the hassle involved in replacing LB7 injectors, most of which involved getting to the injectors in the first place. The new turbo was a variable geometry unit, and the combination of upgraded injectors and the new turbo likely accounted for the bump in power to 310 hp and 605 lb-ft of torque at its best. The LLY's turbo is also notable for being the largest turbo ever on a Duramax engine, bigger than even the cutting-edge L5P's.

Despite solving the injector issue, the LLY seemingly introduced a new one. The engine allegedly tends to overheat, especially when towing; enthusiasts often blame this on an overly restrictive turbo mouthpiece. The LLY also introduced an exhaust gas recirculation (EGR) system across the board for Duramax engines to help keep emissions under control. While not everyone is a fan of EGR, the LLY's EGR system was at least quite reliable.

The Duramax engine saw its biggest power boost up to that point when GM debuted the third-generation Duramax LBZ. This was the first major update to the Duramax engine, with GM engineers introducing a range of improvements to the company's diesel offering. These included a thicker engine block with more webbing in the bearing regions, sturdier forged steel connecting rods, and a fuel injection system that ran at higher pressure than the previous system. GM also specced new cast-aluminum pistons to reduce the engine's compression ratio.

These changes meant that the refreshed Duramax now had 360 hp and 650 lb-ft of torque when paired with a new six-speed Allison automatic transmission that debuted in GM's heavy-duty trucks alongside the new engine. GM also addressed the LLY's overheating issues, with a new, freer-flowing turbo inlet reducing intake and exhaust pressures. The LB7 was also the last Duramax not to run a diesel particulate filter (DPF), an emissions-reducing technology that has the unfortunate side-effect of reducing fuel economy. So, LBZ-equipped GM trucks are something of a hot commodity amongst diesel and Duramax fans.

This doesn't mean that the LB7 is perfect, of course. The new cast-aluminum pistons that GM introduced to the LBZ are known to crack, although this is admittedly only at higher power levels. Stock engines seem to be some of the most reliable V8s ever, as the couple who put 1.2 million miles on their LBZ can attest to.

GM followed the LBZ up quickly with the LMM, which debuted alongside its new GMT-900 pickup platform. The LMM didn't bring much new to the table in terms of horsepower, with a minor bump to 365 hp and 660 lb-ft of torque in trucks like the GMC Sierra 3500HD.

But the LMM wasn't about big numbers: Instead, it was very likely GM's response to new diesel emissions regulations that the U.S. EPA introduced in 2007. The engine was the first-ever Duramax to have a DPF, which trapped and burned off excess soot from the combustion process to reduce emissions. Unfortunately, adding a DPF had the unfortunate side-effect of harming fuel economy due to the extra fuel needed to burn off all the trapped soot (via a process called regeneration).

But worse fuel economy wasn't the only issue that faced the LMM and owners of LMM-equipped trucks. The DPF regeneration process also required owners to drive their trucks above 30 mph for at least 30 minutes, and failure to do so could lead to problems with the filter. Clogged DPF filters, no matter the engine, can increase fuel consumption even further, reduce engine power, and lead to potential turbo problems. Thus, owners consider the LMM a less reliable engine than other Duramaxes. Despite that, the LMM had the longest production run of any Duramax engine thus far, with four years' worth of GM trucks sporting the V8.

The mid-2000s and early 2010s were all about how GM (and other diesel manufacturers) worked with and around diesel emissions regulations. If raw horsepower was anything to go by, the LML was a triumph in that department, managing to crank power up to 397 hp and 765 lb-ft of torque despite the U.S. EPA introducing stricter emissions regulations in 2011.

GM achieved this by introducing components such as a high-pressure fuel pump and new Bosch injectors alongside upgraded pistons, a new variable vane turbo, and lighter internals. GM also introduced a selective catalytic reduction (SCR) system to the Duramax and added a ninth fuel injector specifically for the DPF regeneration process. The result was an emissions-compliant engine that was both more powerful and more fuel efficient than the outgoing model, its claimed 15 city mpg besting the LMM's roughly 12 mpg. The engine was a hit, and GM built more than 600,000 LMLs over the its five-year production run.

But as with all previous Duramax engines, the LML had one notable weak point. This time, it was the turn of the new fuel pump. While it generated more fuel pressure than the previous pump, the new Bosch offering was allegedly quite sensitive to damage from contaminants, potentially leading to a nasty repair bill.

GM also built a detuned version of the LML for chassis cabs and box-delete trucks. Codenamed LGH, the engine made 335 hp and 685 lb-ft of torque for the first couple of years before GM dropped the numbers to 260 hp and 525 lb-ft for the rest of the run.

Now we come to the latest and greatest iteration of the 6.6-liter Duramax V8, the L5P. First produced in 2017, the L5P is now the longest-lived version of the bunch — and even got a recent refresh, with GM updating the engine for even more power in 2024. But let's not get ahead of ourselves and start from the beginning.

When the original L5P debuted, the automotive press hailed it as a complete revamp of the Duramax engine, with new or modified parts throughout. It wasn't all talk, either: the L5P had a bevy of new and upgraded parts including a new cylinder block, an upgraded rotating assembly, a Borg-Warner (instead of Garrett) turbo, a new fuel pump, new Denso fuel injectors, and ceramic glow plugs. GM also upgraded the Allison transmission with new internals to pair with the L5P for the first few years before debuting an all-new 10-speed Allison in 2020.

All these upgrades made for a huge power boost for owners of L5P-equipped heavy-duty trucks, to the tune of 445 hp and 910 lb-ft of torque. This was by far the most powerful Duramax engine thus far, but GM wasn't done. GM engineers kept working on the L5P and the automaker debuted an updated L5P in 2024 boasting improvements to areas such as the turbo, cylinder heads, and fuel delivery. The result was 470 hp and 975 lb-ft of torque in trucks like the 2024 GMC Sierra HD AT4X. GM's come a long way since 2001, that's for sure.

Until recently, the big 6.6-liter V8s we've been discussing were the only engines in GM's mainline Duramax family. But that changed in 2019 when the automaker introduced the 3.0-liter, inline-six LM2. The LM2, a mid-year offering for GM's light-duty Chevrolet Silverado and GMC Sierra pickups, debuted with 277 hp and 460 lb-ft of torque.

Mirroring the big-boy Duramax LB7's debut nearly two decades earlier, this was a notable increase over the offerings from GM's rivals. Ford's contemporary six-cylinder offering, for example, made 250 hp and 440 lb-ft of torque. The clean-sheet design also made the same amount of torque as the 6.2-liter LS3 V8 that GM offered in the Silverado at the time without sacrificing weight or better fuel economy. The latter is one of the baby Duramax's strong suits, and a big plus point in its favor compared to the 6.6-liter Duramax engines.

One notable aspect of the LM2 was that it lacked a conventional DPF as seen on the larger Duramax engines. Designing the engine from scratch meant that GM's engineers could combine the DPF and SCR systems into a unified system they called the SCRF, which improved the regeneration process. The LM2 also had a dual EGR system and somewhat more advanced recirculation system that was better integrated into the SCRF, allowing for better turbo efficiency and emissions control in general. GM built the LM2 for three years until tightening emissions regulations forced the automaker to discontinue it in 2024.

If we've learned anything, it's that GM isn't the sort of company to let government regulations stop it, and that's exactly what happened with the 3.0-liter Duramax. GM had a replacement for the much-loved 3.0-liter LM2 engine ready to go in the form of the LZ0, which started appearing in its light-duty trucks sometime in 2023.

The headline upgrade from the LM2 to the LZ0 is the power numbers, which increased to 305 hp and 495 lb-ft of torque. GM also improved the engine's fuel efficiency ever so slightly, with the LM2's 26 city mpg (in four-wheel-drive mode) climbing to 27 mpg; not a huge deal, admittedly, but improved efficiency is always nice to see. The power and efficiency improvements, slight as they are, are likely the result of changes such as a redesigned combustion bowl, steel — instead of aluminum — pistons, and new fuel injectors.

GM also improved the LZ0's cooling system and extended the oil belt's service interval to 200,000 miles. The latter's roughly 150,000-mile lifespan was one of the main pain points of the LM2, not least because of the pricey repairs. The LZ0 does nothing to address the latter, but owners should at least get another 50,000 miles of use before having to fork out the money to replace the belt.

This even smaller Duramax isn't technically part of the main family, since it has more in common with the VM Motori engine used in the 2008 Jeep Cherokee CRD than anything we've discussed thus far. But since it bears the Duramax name and made its way to the U.S., we figured we'd discuss it anyway to be thorough.

Not only is the LWN not quite a genuine Duramax, it isn't even the original version of the 2.8-liter inline-four. For that, we have to look at the XLD28 engine, which made 180 hp and 346 lb-ft of torque in the global-market 2012 Chevrolet Colorado when specced with a six-speed auto. GM eventually brought the XLD28 to the U.S. market Chevy Colorado as the LWN in 2016. The LWN was more than just a renamed XLD28, though: Engineers spent the four-year gap improving the engine's noise, vibration, and harshness characteristics and reducing exhaust emissions to meet the U.S.' stricter standards. Torque climbed to 369 lb-ft in the process, while horsepower inched upward to 181 hp.

GM stopped offering the 2.8-liter Duramax LWN starting with 2023 models like the 2023 Chevrolet Colorado ZR2, replacing it with a more powerful 2.7-liter Turbo Plus engine. However, the LWN engine lives on in the Brazilian-market Chevrolet S10, where it makes 205 hp and 376 lb-ft of torque as of 2024 thanks to improvements such as new aluminum pistons, increased fuel pressure, and redesigned fuel injectors.