Duramax LML Vs L5P |10 Differences and Similarities

In case you are wondering what the difference between LML and L5P engines is, this article will certainly be of great help to you in understanding which is the better and more reliable engine.

Duramax LML was the predecessor of the L5P engine.

Duramax LML engines were manufactured from 2011 to 2016, and Duramax L5P engines have been manufactured since 2017.

There are a few major and minor differences between Duramax LML and L5P diesel engines.

LML and L5P Duramax Background Information

1. Duramax LML

GM manufactured the LML engine which is also called LML Duramax, for heavy duty diesel vehicles.

It was developed by GM and Isuzu as a product of their partnership program.

They started the collaboration in 2000 and introduced Duramax LML in 2011.

It is the first engine of the Duramax family engines which had significant advancement over the predecessors.

Fuel injection system of high pressure common rail intensified the fuel efficiency and reduced emissions.

Power output and throttle response were improved with an upgraded turbo charge system.

2. Duramax L5P

GM developed the L5P or 6.6L V8 Duramax engine for heavy duty wheels.

It was an upgraded version of the LML Duramax and GM used the engine in 2017 GM vehicles.

L5P has better performance, durability and fuel efficiency compared to older engines.

It is a powerhouse and can generate 445 hp with 910 lb-ft of torque.

With that beast, GM heavy trucks can tow heavy loads and trailers effortlessly.

Advanced exhaust system of the engine reduces emissions without losing performance.

Duramax LML Vs L5P [10 Differences]

Duramax LML and L5P have 10 basic differences, including pricing, horsepower, vehicle application, durability, mpg, mph, warranty, longevity, towing capacity, etc.

01. Vehicle Application

Recent GM vehicle models come with a Duramax L5P engine, while 2011 to 2016 models are equipped with a Duramax LML engine.

Duramax LML engine is used in the following vehicles:

  • Chevrolet Silverado HD (2011-2016)
  • GMC Sierra HD (2011-2016)

Duramax L5P engine is used in:

  • Chevrolet Silverado HD (2017 and newer)
  • GMC Sierra HD (2017 and newer)

02. LML Vs L5P Specs

The Duramax LML and L5P engines use the same displacement of 6.6 liters or 402.7 ci.

Both consume diesel fuel to generate energy.

Also, they have the same compression ratio of 16:1.

The engine block is made of cast iron, and both engine heads are made of aluminum.

The crankshaft and camshaft are also made of forged steel and steel.

Both engines have almost the same specs.

03. Horsepower

The Duramax 6.6L LML V8 engine produces 397 hp or 204 kW at 3,000 RPM.

The Duramax 6.6L L5P V8 engine produces 445 hp or 332 kW at 2800 RPM.

Duramax L5P diesel produces 48 hp more than Duramax LML in terms of power output.

04. Torque

The Duramax LML diesel engine provides 765 lb-ft or 1037.2 Nm of torque at 1600 RPM.

While the Duramax L5P diesel engine provides 910 lb-ft or 1233.79 Nm of torque

The L5P Duramax diesel engine provides up to 145 lb-ft or 196.5 Nm more torque than the LML engine.

05. Mileage

LML engines get 24 mpg on the highway and 15 mpg in the city.

Duramax L5P V8 gets 20 mpg on the highway and 15-16 mpg in the city.

As far as MPG is concerned, the Duramax LML is the champ.

06. MPH

A Duramax LML engine can accelerate from 0-60 in about 5.6 seconds.

Duramax L5P engine accelerates from 0 to 60 mph in 7.1 seconds.

The LML engines reach 0-60 mph 1.5 seconds faster than the L5P engines.

So MPH-wise, Duramax LML wins.

07. Towing Capacity

The Duramax LML engine has a standard towing rating of 14,500 pounds, but it can pull up to 18,000 pounds with a 5th wheel.

A Duramax L5P engine has a standard towing capacity of about 20,000 pounds, while its maximum 5th-wheel towing capacity is 23,100 pounds.

So Duramax L5P is better at towing than LML.

The L5P can tow up to 5,100 pounds more than the Duramax 6.6L LML engine.

08. Pricing

Depending on the year, a Duramax LML engine might cost between $13,500 and $15,000.

The L5P engine costs around $16,500.

That means L5P is about $1,500 more expensive than LML.

09. Warranty

A GM engine is generally covered by a 05-year or 50,000-mile warranty.

Although the period and range of the warranty can vary from engine to engine.

10. LML Vs L5P Reliability

GM’s L5P and LML engines are reliable.

But if we compare LML and L5P, the L5P engine is more reliable than the LML engine for a few reasons.

L5P is the upgraded generation of LML engines.

Because of the cranking piston issue in the LML engine, its towing capacity is reduced compared to the L5P engine.

The cranking piston issue with the LML engine makes it less reliable than the L5P engine.

A Duramax LML diesel engine lasts around 300,000 miles, while a Duramax L5P diesel engine lasts around 350,000.

User reports say the Duramax L5P crossed 500,000 miles with no problems.

That’s what makes the L5P engine more reliable than the LML.

Which is Better LML or L5P?

LML and L5P engines have advantages and disadvantages, so we need to compare them to understand which is better.

GM 6.6L LML Duramax Diesel Engine


  • Fuel-efficient compared to L5P
  • Last over 300,000 miles


  • Have DEF pump failure problem
  • Injection pump issues
  • NOx sensors failure issue

GM 6.6L L5P Duramax Diesel Engine


  • L5P has a higher power output than other Duramax engines
  • Fewer issues
  • Compared to other Duramax engines, L5P is more reliable


  • Fuel injector failure problem
  • MAP sensor problem
  • Allison 1000 power limitation

When we compare the advantages and disadvantages of L5P and LML, it is clear that the L5P engine has fewer disadvantages than the LML engine.

Here’s a video explaining the differences between LML and L5P:


Is the LML or L5P a Better Motor?

Due to higher power output, better performance, and better comfort, the Duramax L5P has a better motor.

However, it has problems like MAP sensor failure, fuel injector, transmission issues, etc.

Is the LML the best Duramax?

Only the engines with great performance and no shortcomings become the best engine. Duramax LML and L5P both are great engines but they have some scopes for improvement. Both of them have the potential to become the best engine and they are already one of the best engines of GM.

Is the 2024 Duramax a L5P?

Yes. Duramax’s 2024 engine is an L5P 6.6L engine. It has got a new turbocharger, better pistons, enhanced high pressure fuel system, calibrations, etc.

What is high mileage for a LML Duramax?

Duramax engines are well known for reliability and performance. Usually, they last up to 300 thousand miles. Some users have 450,000 miles on their Duramax vehicle. More than 300,00 miles is high mileage for a LML Duramax.

What Goes Wrong on LML Duramax?

The LML Duramax has some sensor and emission issues.

Due to the cost involved, many users hesitate to repair or replace these components.

What Does L5P Mean on a Duramax?

General Motors’ L5P Duramax is a turbodiesel engine designed to power heavy-duty (HD) pickups.

This engine is part of the new generation of Duramax engines, displacing 6.6 liters and replacing the 6.6 L Duramax V-8 LML.

How Long Do LML Injectors Last?

Duramax LML injectors last between 90,000 and 100,000 miles.

Injectors usually last a lifetime.

Injectors require regular maintenance to last a lifetime.

Final Thoughts

Undoubtedly, the LML and L5P Duramax diesel engines were excellent for their respective eras.

L5P is better than LML if you’re forced to choose between the two.

Want to explore the differences between other engines? Read the following articles:

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