The Duramax engine is a diesel-powered motor that was originally introduced in 2001. With more than two million produced, it’s wise to know the best and worst years of the Duramax engine because they aren’t all reliable.
In this guide, we outline the best Duramax model years so you can ensure you have a reliable truck. We also list the worst Duramax model years, giving you advice on which ones to avoid, show you the most common problems and answer your top diesel motor questions.
The Best Duramax Engine Model Years
Through the years, there have been many variations of Duramax engines, with some more reliable than others. After our research, we feel comfortable recommending the 2010-2017 LGH, 2017-2023 L5P, 2019-2023 LM2 and the 2014-2022 LWN.
Let’s take a closer look at these Duramax engines, their best features and the vehicles they are equipped in.
1. 2010–2017 Duramax LGH
Enthusiasts can’t get enough of the LGH turbo Duramax. It’s powerful, efficient and highly durable. With an improved casting, it creates a quieter experience than previous models. The strong cast iron base is said to last for many years.
With a die-cast aluminum crankcase on the lower engine, the block is completely protected. Plus, Piezo injectors ensure accurate fuel metering, even at lower injection rates. The result of this is a smooth idle and reduced combustion noise. Finally, the variable-vane turbocharger puts out more power with less exhaust.
Vehicles equipped with Duramax LGH engine:
- Chevrolet Silverado 2500/3500
- GMC Sierra 2500/3500
- Chevrolet Express 3500/4500
- GMC Savana 3500/4500
2. 2017–2023 Duramax L5P
The latest version, the L5P, has the best efficiency. There are major technological advancements that make this the diesel motor of the future. While we don’t have enough long-term data on these diesel motors yet, the initial reports from the past few years are good.
Most importantly, the L5P is the most powerful Duramax to date. It pumps out 445 horsepower and boasts of more than 900 lb-ft of torque. There’s no lack of power with this motor.
Vehicles equipped with the Duramax L5P engine:
- Chevrolet Silverado HD
- GMC Sierra HD
3. 2019–2023 Duramax LM2
The baby Duramax, as it is known, is also a top contender, especially if you don’t need maximum power. This 3.0L I6 turbodiesel produces 277 horsepower and 460 lb-ft of torque. With an EPA rating of 26 mpg combined, it’s also the most efficient.
The LM2 engine is no slacker. It can tow up to 9,000 pounds, which suits most drivers. It also pairs with a ten-speed automatic for complete control.
Vehicles equipped with the Duramax LM2 engine:
- Chevy Silverado 1500
- GMC Sierra 1500
- Chevrolet Tahoe
- Chevrolet Suburban
4. 2014–2022 Duramax LWN
The LWN contains a variable-geometry turbo to create better power without sacrificing efficiency. It’s rated for 181 horsepower and 369 lb-ft of torque, making it perfect for midsize vehicles. Of all the diesel engines that GM has produced, this is the cleanest, adhering to all of the EPA regulations.
With its broad torque band, this smaller engine is extremely potent. Performance is reliable and it’s a great addition for anyone needing a reliable way to tow or haul.
Vehicles equipped with the Duramax LWN engine:
- Chevrolet Colorado
- GMC Canyon
- Chevrolet Express
- GMC Savana
Worst Duramax Engine Model Years
While the Duramax engines seem to be mostly reliable these days, the earlier years exhibited a lot of problems. We can’t recommend the 2001-2004 LB7, the 2004-2005 LLY, the 2006-2007 LBZ, the 2007-2012 LMM, or the 2011-2016 LML.
Take a look at the most common complaints about these Duramax engines.
1. 2001-2004 Duramax LB7
The LB7 is the very first V8 Duramax. The 6.6L V8 has a cast iron engine block with aluminum heads that makes for a durable design, yet because it’s brand-new, there were some faults. Some users complain about leaking fluids.
However, the worst complaint is injector failure. After just 100,000 miles, it became common for the injectors to fail. There are also reports of defective water pumps and overheating.
Vehicles equipped with the Duramax LB7 engine:
- Chevrolet Silverado 2500HD & 3500
- GMC Sierra 2500HD & 3500
2. 2004-2005 Duramax LLY
This second-gen V8 diesel engine was only around for a short time. Sadly, it isn’t much different from the LB7, with no major improvements. With that said, GM did resolve the injector issue with this motor.
Still, the engine is prone to overheating while hauling heavy loads or if the ambient temperatures get too hot. A faulty air intake seems to be the root of the trouble. With the poor construction, the engine can’t get enough air. Some people resolve the issue with an aftermarket air intake, but who knows what damage has been done to the motor before this is installed.
Vehicles equipped with the Duramax LLY engine:
- Chevrolet Silverado HD
- GMC Sierra HD
- Hummer H1 Alpha
3. 2006-2007 Duramax LBZ
The LBZ was released as a replacement for the LLY, but its lifespan was also short. It contains a thicker engine block than the LLY and fuel injection pressure is better. This is also the final year before modern emission control systems were installed, which inevitably leads to more problems. After two years of production, this model was shut down because of the strict emissions regulations by the EPA.
From a mechanical standpoint, there are serious concerns with the pistons. Anyone looking to modify the engine has to worry about the pistons cracking. It’s also common to experience glow plug failure with these engines.
Vehicles equipped with the Duramax LBZ engine:
- Chevrolet Silverado HD 2500/3500
- Chevrolet Kodiak
- GMC Sierra HD 2500/3500
- GMC TopKick
4. 2007-2012 Duramax LMM
The LMM has a much longer run and replaced the LBZ. There were some improvements, with a heavy focus on emissions. Yet, there was still the problem of the pistons cracking if any tuning was performed.
The updated engine also suffers fuel system failures and the paired transmission often has leaky lines. Furthermore, there are reports of a blocked DPF system.
Vehicles equipped with the Duramax LMM engine:
- Chevrolet Silverado HD
- GMC Sierra HD
- Chevrolet Express
- GMC Savana
- Chevrolet Kodiak
- GMC TopKick
5. 2011-2016 Duramax LML
At first, enthusiasts were hopeful about the LML, with improvements that looked promising. After just a short time with it, drivers realized that this engine wasn’t what they thought.
The biggest failure seems to be the fuel system, most importantly, the fuel injection pump, which fails often. Because of the defect, fragments ended up in the engine, leaving owners with massive repair bills.
Vehicles equipped with the Duramax LML engine:
- Chevrolet Silverado HD
- GMC Sierra HD
Most Common Duramax Engine Problems
Across the board, it seems that many of the defective Duramax engines deal with the same problems. They are known for fuel injector failure, a defective water pump, turbocharger oil ingestion and glow plug failure.
Here are some more details about each of these problems.
Fuel Injector Failure
Failure of the fuel injectors is common across the board but most prevalent with the LB7. Premature failure led to many expensive repair bills for owners.
GM was never oblivious to the issues. In fact, there were some recalls issued to deal with the design flaws on several models.
Defective Water Pump
Several different Duramax engine lineups dealt with water pump failure, but none were as common as the LB7 and LLY. Considering the water pump is required to keep the engine cool, many drivers struggled with overheating engines.
If repaired early enough, there weren’t any other problems. However, some people let it go and ruined the motor. Down the road, GM addressed the issue by redesigning the water pump in future engines.
Turbocharger Oil Ingestion
Sadly, the turbocharger problems affected many different 6.6L Duramax engines. You can find reports of it with the LB7, LLY, LBZ, LMM and LML models.
The fault lies in the PCV design, where excess pressure vents to the intake. Because of this flaw, oil is supplied to the turbocharger, leading to failure.
Glow Plug Failure
While it may not seem as big of a deal as the other issues, several Duramax engines suffered from glow plug failure. Most commonly, this problem occurs with the LLY and LBZ motors.
The underlying issue is the design of the glow plug modules, leading to failure. While GM did issue some recalls, it doesn’t change the fact that there are tons of these trucks out on the road ready to fail a driver.
What is the most reliable Duramax year?
The modern Duramax engines seem to be among the most reliable. Starting in 2010, the LGH won a lot of respect for having fewer mechanical difficulties. This engine was used through 2017. We also recommend the 2017-2023 L5P, the 2019-2023 LM2 and the 2014-2022 LWN if you want a diesel engine that’s going to last.
What is the high mileage for a 6.6 Duramax diesel?
In general, diesel engines tend to last far longer than gasoline engines unless there are mechanical design flaws. For the most part, Duramax diesel engines last to 300,000 and beyond. A well-maintained Duramax engine that’s considered a reliable model should make it nearly 500,000 miles without any major concerns.
Which Duramax has injector problems?
The very first Duramax built, the LB7 (2001-2004), seems to have the most trouble with fuel injectors. To avoid problems, owners can install aftermarket injectors that resolve the design flaw, but these older trucks may not be worth putting more money into. You also won’t know how well the truck was cared for by its previous owners.
What is the strongest Duramax engine?
The most powerful Duramax V8 engine is the L5P. It’s the most recent model and was introduced in 2017. With the ability to pump out 445 horsepower and 910 lb-ft of torque, this engine is meant for heavy jobs. It’s also considered to be one of the more reliable Duramax engines ever installed in GM trucks.
If you are looking to acquire a GM vehicle with a Duramax engine in it, you should always do your research first. With more than two million of these engines installed across the years, there are plenty that are worth your money and some that are only going to cost you more. In general, the earlier models are going to give you the most problems.
Read through customer reviews and online forums to see what other people think. It’s also smart to ask the seller of the vehicle if there are service records. The better an engine is cared for, the more likely it is to keep running without any major repairs. When it comes to reliable diesel engines, you may even get 500,000 miles out of it with no incidents to complain about.
Tags: Duramax
Categories: General
