What Is The Best Duramax Engine? Explained

There are certain Duramax models that are more effective, efficient, and durable than others, but not all of them deliver satisfactory results. You must know which Duramax engine is the best if you want to get the performance you expect from it. LBZ 06-07 is widely considered to be the best Duramax engine of all time by many automotive experts.

What Is The Best Duramax Engine Explained

What is The Best Duramax Engine? (Model Years)

It’s necessary to discuss the pros and cons of the different Duramax engines before drawing a conclusion about which is the best. Duramax engines have at least one good and one bad point in every variant. Popularity varies from engine to engine. Duramax engines made prior to emissions between 2001 and 2007 are highly coveted for their high reliability.

What is The Best Duramax Engine (Model Years)

 In contrast, more modern engines have a higher horsepower, torque, and upgrade capability due to the use of Duramax performance parts.

LB7: 2001 – 2004

It was the LB7 engine that introduced Duramax in 2001. There is still a great deal of interest in it on the used market. Aside from the LB7 engines sold in California, none of these engines had emissions controls. Engines with these extra emissions parts were highly reliable because they lacked them.

In modern Duramax engines, emissions devices often have problems, and they typically last for a very short period of time. Most of the LB7’s internals are rock-solid, including the block. There is only one weakness with the LB7, and that is cracked or leaky injectors.

 The good news is that many of the old problems with the LB7 can easily be resolved with modern Duramax diesel parts. You might find that any weak or failing parts have already been replaced if you look at one now.

LLY: 2004.5 – 2006

The LLY Duramax engine is one of the shortest-lived Duramax engines. Its structure, parts, and lack of emissions control are very similar to those of the LB7. In comparison to other Duramax engines except the most recent model in the L5P , the LLY is capable of producing the most horsepower through tuning alone. As far as weaknesses go, the LLY traded injector issues for overheating issues and blown head gaskets caused by heavy-towing. In contrast to bad injectors, head gaskets are relatively cheap and easy to repair.

LBZ: 2006 – 2007

As short as the LLY’s run was, the LBZ’s run was even shorter. The LBZ is one of Duramax’s most popular engines, despite lacking emissions control devices. A variety of Duramax parts mods and tuning offer the best potential for adding performance and horsepower.

In addition to being strong and durable, the LBZ engine also has a high level of reliability and power. Over 600 horsepower is known to crack the pistons, which is the only weakness. In most cases, owners don’t have to worry about this because getting to that level takes some $20,000 in modifications and isn’t necessary for the majority.

LMM: 2007.5 – 2010

As Duramax introduced its emissions control devices, the LMM was nearly identical to the LBZ. An oxidation catalyst, a diesel particulate filter, and an exhaust gas recirculation system are included in the package. Known failure points in this engine include all three of these components.

Due to the exhaust treatment’s use of fuel, this engine also had lower fuel efficiency. Despite its power and reliability, the engine features the same characteristics as the LBZ.

LML: 2011 – 2016

With almost 400 horsepower stock and 765 pound-feet of torque, the LML Duramax engine offered a huge leap in performance from the previous engine. The block, rods, pistons, and main bearing were strengthened to accommodate this massive power increase.

Compared to the previous engine, this engine no longer uses a high-pressure fuel pump to control emissions. Tuning or bolt-on modifications are limited by the smaller pump. For most owners, power-gain mods aren’t necessary because the LML is already powerful out of the box. Generally, this engine is reliable and great for towing. A major disadvantage is the limited amount of tuning you can do.

L5P: 2017 To Present

In 2017, Duramax launched the L5P, the newest generation of the engine. There are 445 horsepower and 910 pounds-feet of torque, which are upgrades from the previous model. The main difference between the L5P Duramax and the L5P is the addition of cast-aluminum heads for increased airflow.

The L5P features a lift pump, which is a major improvement. As a result of this new part, the main HPFP is less stressed, resulting in increased horsepower and fuel system reliability.

Even though the L5P is still relatively new, all signs indicate that it is capable of good tuning and modification. While the L5P looks reliable on paper, it hasn’t been on the road long enough to prove how durable and reliable it is.

Types Of Duramax Engines

Duramax engines are classified into various types based on their best features as follows:

Types Of Duramax Engines


The best Duramax engines for flexibility are the LML 07.5-10 and the LLY 04.5-06. There is a larger turbo on the LLY. It is possible for this engine to overheat and develop head gasket issues over time, however. As with the LBZ, the LML is quite similar, but it has a DPF and increased horsepower for improved performance. For vehicles from this era, DEF and DPF may cause some problems for the engine.


You can opt for the LBZ engine if you prefer an engine without emissions devices, such as DPF. A few minor modifications, such as changing the cold air intake, enable this engine to deliver increased horsepower.

There was a crossover year for the LBZ and LLY in 2006. LLY 2006 is a better option than LBZ 2006. There are, however, no replacement parts for LLY. Check the transmission to determine compatibility. A 6-speed Allison is referred to as a LBZ, while a 5-seed is referred to as a LLY.

Complete Stock

The LBZ 06-07 Duramax engine is the best Duramax engine for leaving fully stocked and driven. There is no regeneration cycle needed with this engine since it is pre-DPF. As well as the EGR system and catalyst, the engine has an exhaust gas recirculation system.

Heavy Towing

For towing heavy objects over long distances, Duramax L5P 17 through current and LML11-16 are the most suitable engines. Power and chassis are superior to older models with these engines. There are no major issues with the L5P engine since it is fairly new.

Best for Modification

Choose the LB 01-04 if you are looking for the best engine to build your powerhouse. You may need to replace certain parts on this engine to make it capable of supporting extreme demands, including the injector and head gasket.

LBZ 06-07 Duramax Engine

Many automotive experts consider the LBZ 06-07 to be the best Duramax engine, and their reasoning makes sense. The 2002 engine doesn’t overheat as much as the 2004 model nor does it have injector problems like the 2001 model. Therefore, the engine saves a significant amount of money compared to repairing it. There are also not many problems with emissions with the LBZ 06-07. Furthermore, the engine’s reliability makes it worth buying.

In spite of this, the pistons of this engine have a tendency to crack, especially when providing high horsepower outputs. Besides being quite expensive, this engine has the best engine tag as well. If you want a long-lasting and low-maintenance engine, the 06-07 Duramax is worth considering.

Avoid these Duramax engine model years

In terms of Duramax model years, the following are the worst:

  • Duramax LB7 2001 – 2004
  • Duramax LLY 2004 – 2005
  • Duramax LBZ  2006 – 2007
  • Duramax LMM  2007 – 2012

To put it simply, you should avoid older Duramax engines manufactured between 2001 and 2010. There is a greater improvement in performance with the newer models. In 2001 – 2004, Chevrolet Kodiak, GMC Sierra HD, and GMC Topkick, GM Authority produced a 6.6L Duramax engine. Neither recirculation of exhaust gases nor diesel particulate filters were installed in the engine.

It is also recommended to avoid the LB77 model due to fuel injection system problems. Generally, Duramax engines are available on GMC Sierra HD, Chevy Silverado, Chevy Kodiaks, and GMC Topkicks.

Hummer H1, 2004 – 2005 Chevrolet Silverado, and GMC Sierra HD are equipped with Duramax LLY engines, which overheat during heavy towing. Owners of the vehicle complain about blown head gaskets.

In spite of having addressed the blown gasket and overheating issues, the LBZ engine’s piston cracks at higher horsepower levels. Due to salt and high humidity in northern areas, owners also complain that their rocker panels and cab corners rust out quickly.

At higher horsepower, the LMM engine is equipped in Chevy Silverados, Savannas, Kodiaks, GMC Topkicks, and Sierra HDs. A failure point is also present in its DPF.

Duramax Engine Longevity Expected

Duramax engines are exceptionally reliable by default and last for thousands of miles when maintained properly. It is not uncommon to see classic cars on the streets that still work like new after thousands of miles. The Duramax diesel engine has been reported to reach up to 200,000 miles without showing any signs of wear and tear.

You may be able to run your engine for around 400,000 miles if you take care of it properly. A Duramax diesel engine can also run 535,050 miles without needing to be serviced. The Duramax engine is usually expected to last between 200,000 and 300,000 miles on average before experiencing any major problems.

In addition to the make and model of the vehicle, driving style, skills, and amount of maintenance, the exact longevity of a diesel engine will differ.


Is LB7 Better Than LLY?

In terms of emission controls, the LB7 Duramax engine is superior to the LLY Duramax engine, which has the largest turbocharger. A diesel particulate filter is included in the LMM engine, and the LBZ engine also receives plenty of improvements.

Is General Motors Discontinuing the 3.0 Duramax Diesel?

Chevy Suburban, Chevy Tahoe, Cadillac Escalade, and GMC Yukon will be equipped with GM’s 3.0 turbo diesel Duramax engine in 2023. However, the manufacturer announced that the Duramax 3.0L engine wouldn’t be available for these vehicles. Read More: 3.0 Duramax Problems Explained

Why is Duramax Better Than Cummins?     

There is a maximum power of 445 HP in a Duramax engine, and 420 HP in a Cummins engine. It is important to consider horsepower when purchasing a heavy-duty vehicle. There is no comparison between the Duramax engine and the Cummins engine in this case.


If you’re looking for a Duramax diesel that offers everything you need, the LBZ is hard to beat. A significant improvement was made to the injectors and head gaskets on the LBZ engine over the previous two engines. Diesel enthusiasts find the LBZ extremely attractive because of its excellent tuning and modification potential.

 A final advantage of the LBZ is that it is the last generation of Duramax without emissions control parts, which makes it highly reliable. This makes the LBZ our best choice for Duramax engines.

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