10 Differences Between Duramax LML Vs L5P and Which One is Better?

Regarding diesel engines, Duramax has been a well-known and highly respected name in the industry for many years. Two of the most popular Duramax engine models are LML and L5P. While both engines have unique features and benefits, some significant differences can improve one, depending on your needs. In this blog, we’ll look at 10 key differences between Duramax LML vs L5P engines to help determine which suits your specific requirements better.

Duramax LML Vs L5P [10 Differences]


The Duramax engine is known for its reliability and performance. Two of the most popular versions of this engine are the LML and L5P. Both engines have unique features that set them apart from each other. Let’s discuss 10 differences between the two engines – LML Vs L5P.

Vehicle Application:

The LML engine was first introduced in 2011 and was used in Chevrolet Silverado HD and GMC Sierra HD trucks until 2016.

The L5P engine was released in 2017 as a replacement for the LML and is currently used in 2020-21 Chevrolet Silverado HD and GMC Sierra HD trucks.

LML Vs L5P Specs:

When comparing the LML and L5P engines, it is evident that they share a common displacement of 6.6 liters or 402.7 ci and use diesel fuel to produce power. They boast a compression ratio 16:1 and feature an engine block made of cast iron and aluminum engine heads.

The crankshaft and camshaft are forged from steel in both engines, and their specifications are nearly identical. Therefore, regarding LML vs L5P, there are many similarities between the two engines.


At 3,000 RPM, the Duramax 6.6L LML V8 engine generates 397 hp or 204 kW, while the Duramax 6.6L L5P V8 engine produces 445 hp or 332 kW at 2800 RPM. Regarding power output, the Duramax L5P diesel engine produces 48 hp more than the Duramax LML.


The Duramax LML produces anywhere from 397 to 445 horsepower and between 765 and 910 lb-ft of torque. This exceptional power output makes it one of the strongest engines in its class, with enough strength to handle even the heaviest loads. Whether you’re hauling a trailer or need extra power for acceleration, there’s no doubt that the Duramax LML can get the job done.

The L5P engine boasts a maximum torque of 910 lb-ft at just 1600 RPM. The L5P provides tremendous pulling power at low RPMs, making it an ideal choice for heavy-duty trucks and towing applications.


According to official EPA ratings, the LML v8 engine in a Chevy Silverado 1500 truck gets an average of 16 mpg in the city and 22 mpg on the highway. So, these numbers are just estimates based on laboratory tests and may not reflect real-world conditions. In reality, the actual mileage of an LML-powered vehicle can vary widely depending on how it’s driven.

Aggressive acceleration or high-speed cruising can quickly burn through fuel while maintaining a steady speed at lower RPMs can improve fuel economy. If your Duramax gives bad fuel mileage, then guaranteed, you should visit the mechanic.

The L5P engine’s mileage varies depending on driving conditions, vehicle weight, terrain, and driving habits. On average, it can travel between 17 to 20 miles per gallon on the highway. City driving decreases its fuel efficiency to around 13-15 miles per gallon.


The acceleration time of a Duramax LML engine from 0 to 60 mph is approximately 5.6 seconds, while the L5P engine takes 7.1 seconds to reach the same speed. This means that the LML engine is 1.5 seconds faster than the L5P engine in terms of reaching 0-60 mph. Therefore, regarding MPH, the Duramax LML emerges as the winner.

Towing Capacity:

Towing Capacity:

The LML engine has a standard towing rating of 14,500 pounds, which is no small feat. However, compared to its newer counterpart, the L5P engine’s towing capacity leaves it in the dust.
With a maximum towing capacity of about 20,000 pounds, the L5P engine is designed with heavy-duty hauling in mind. This makes it an ideal choice for those who need to tow large trailers or haul heavy loads regularly.


The Duramax LML engine is an older model that has been in production since 2011. It might cost between $13,500 and $15,000, depending on where you purchase it from.
The newer L5P engine was introduced in 2017 and had more advanced features than its predecessor. It costs around $16,500, about $1500, more expensive than the LML engine.


The Duramax LML engine comes with a standard 05-year or 50,000-mile warranty. GM will cover the cost of repairs or replacements if any issues arise within this period. It’s worth noting that some components may have a shorter duration of coverage under this warranty scheme.

The newer Duramax L5P engine boasts a longer warranty period – 05 years or 100,000 miles. This extended coverage is due to the several enhancements made to this engine model to improve its durability and performance.

LML Vs L5P Reliability:

LML Vs L5P Reliability:

While both GM’s L5P and LML engines are dependable, the L5P is considered more reliable than the LML due to a few factors. As an upgraded generation of the LML, the L5P has addressed the cranking piston issue that limits the towing capacity of the LML.

This issue also makes the LML less reliable than the L5P. While a Duramax LML diesel engine typically lasts around 300,000 miles, a Duramax L5P diesel engine can last up to 350,000 miles. User reports show that some Duramax L5P engines have surpassed 500,000 miles without any issues. Therefore, it’s clear that the L5P engine is more reliable than the LML.

Which is Better LML or L5P?

Which is Better LML or L5P?

Both engines offer impressive power and efficiency, but which one is better? The answer ultimately depends on your specific needs and preferences.

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:



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

Final Thoughts:

The comparison between LML vs L5P shows that the Duramax LML and L5P have unique features that make them stand out in the market. While the L5P is a newer version with advanced engine technology, the LML has proven to withstand the test of time. Ultimately, choosing between these two engines depends on your needs and preferences.

If you’re looking for a powerful engine with high towing capacity and fuel efficiency, the L5P is an ideal choice. On the other hand, if you want a reliable engine that requires minimal maintenance and repair costs, then the LML is an excellent option. It’s crucial to evaluate all aspects of each engine before making a final decision. Happy driving!


Is the LML or L5P a Better Motor?

No “better” motor exists – they are both great options. The LML is slightly more powerful, but the L5P has a longer life.

What Goes Wrong on LML Duramax?

-Engine knocking: This is usually caused by a worn or damaged valvetrain or camshaft. It can be fixed by replacing the parts but it can also lead to engine damage.
-Engine failure: A Duramax engine can fail for several reasons, including worn or damaged parts, faulty fuel injection systems, and over-revving. If the engine fails while you’re driving, it can cause serious injury or even death.

What Does L5P Mean on a Duramax?

L5P typically stands for “low-pressure fuel system.” It’s a system that helps optimize the fuel delivery to the engine and can improve performance and fuel economy.

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