List of Duramax Years to Avoid (3+ Best Options)

This blog will answer the following questions: which year Duramax engines should you avoid? What are models powered by the Duramax engine? What are the best Duramax engines? What are the specifications of the latest Duramax engines?

Duramax engines- which years should you avoid?

The Duramax engines produced in the following years by the Dmax should be avoided, the performance is not great and there are reliability problems.

Production yearsEngine Designation

Let’s take a closer look at problems in each of the production years:


The LB7 engine code 1 is the first engine manufactured by Duramax. The pre-emission control engines are still very sought after in the used car market. LB7 is a 6.6 liter V 8 engine with a cast iron block and an Aluminium head.

It can produce 300 horsepower and uses a direct injection common rail fuel system made by Bosh. The engine has a very good built quality but the problems in the components of the fuel system made it very unreliable.

The direct fuel injection used in the fuel system is likely to develop cracks due to improper design. Due to cracks in the injectors, fuel is not properly injected into the combustion chamber and there is also a combustion misfire.

Back smoke coming from the engine is one of the symptoms of faulty injectors. Duramax updated the design of the fuel injector and the cost of the new part is around 400-450 in the USA. The fuel system in the LB7 uses a common rail to store the diesel under high pressure before it is injected.

There is no high lift fuel pump in the system, only the common rail injection pump is used to pump the fuel. This pump is under extreme starting especially at high engine speeds. The O-rings in the fuel system also leak due to excessive strain.

There are many rebuild pumps available in the market and the replacement job can cost between 600-700 USD including the fuel system O-rings.


From 2004 to 2005, Duramax used the LLY engine. It was also called 8GF1 or engine 2. The LLY is the first engine with emission control systems. LLY also used a variable geometry turbocharger and an exhaust gas recirculation system to keep the NOX emissions low.

One of the major design changes was in the valve covers. Because of the injector problem in the LB7 engine, LLY has access holes to replace the fuel injectors. There is no need to remove the valve covers completely which saves time and labor costs.

The LLY engine has an overheating problem due to the small size of the radiator. The radiator is not capable of cooling the coolant fast enough and as the temperature of the engine starts to rise it fails to supply fresh coolant to the system.

The intake manifold also restricts the flow of charge air, which causes the engine to operate at a higher temperature than the LB7. overheating leads to cylinder head gasket failures and damage to the moving components in the engine.

Another common problem of the LLY is the loss of fuel pressure in the diesel common rail. The fuel pressure in the common rail is regulated by a pressure regulating valve, the spring of the pressure regulating valve gets weaker as the mileage of the engine increases.

The pressure regulating valve starts to leak the fuel in the rail at high pressure, and the leaked fuel is again returned to the fuel tank. The pressure relief valve can cost 150-170 USD, there are a few used ones also available but it is recommended to install a new valve.


The 2006 Duramax engine is very popular for its improved performance map in the engine control unit. The engine output is well over 350 horsepower but the engine has a severe problem with the piston. The piston of the LBZ is known to crack and damage the cylinder block.

Although the compressor ratio of the LBZ is lower than the predecessor, the cast aluminum pistons are not strong enough to withstand an increase in combustion pressure and temperature. As long as the engine is kept running at stock performance, this problem does not occur.

Other issues in the LBZ engine are overheating due to a damaged engine cooling fan, long cranking because of faulty glow plugs and one of the more severe issues is the damaged engine control module.


The LMM engine launched in 2007 featured additional emission control systems like exhaust gas circulation with a cooler and a diesel particulate filter to reduce soot particles in the exhaust. Because of the DPF, the intake manifold also stays clean as the exhaust gasses are mixed with fresh air.

LMM also has a larger radiator to prevent any overheating problems. The LMM engine has problems like low fuel pressure, excessive exhaust back pressure due to a clogged diesel particulate filter, and damage to the moving components of the engine if there are any changes to the performance map.

What are models powered by the Duramax engine?

The models powered by the Duramax engines are given in the table below:

Engine Engine output (Horsepower)Model Names
LB7310 Chevrolet- Kodiak & Silverado
GMC-Topkick & Sierra HD
LLY250-300 Hummer H1 Alpha
Chevrolet-Silverado, Kodiak, Express
GMC Sierra HD
LBZ250-350Chevrolet Silverado, Kodiak
GMC-Topkick & Sierra HD
LMM365Chevrolet Silverado, Kodiak. Express
GMC Topkick, Savana, Sierra HD
LGH335Chevrolet- Express, Silverado
GMC- Savana, Sierra

The LML and L5P engines are high-performance diesel engines. The LML makes 397 horsepower and the L50 makes 445 horsepower. LML was discontinued in 2016 it was available in some of the Silverado and Sierra HD models. 

L5P also has a less powerful L5D engine, it makes 350 horsepower and is found in 2018-2019 Silverado MD models.

What are the best years of Duramax engines?

The Duramax engines produced in the following years are the best. The cast iron with aluminum cylinder head construction is very durable. If the engine is periodically maintained, it can last for 300,000 miles.

  • 2010 -2017 Duramax LGH
  • 2014 to 2016 Duramax LWN 
  • 2017 to 2021 Duramax L5P 
  • 2019 to 2021 Duramax LM2 

What are the specifications of the latest Duramax engine?

The latest Duramax engines are L5P and LM 2, specifications are given in the table below:

Specs/ engineL5PLM2
Horsepower445 hp277 hp
Engine oil capacity9.5 liters6.5-7.0 liters
Compression ratio16.0:115.0:1
Max engine speed 3450 rpm5100 rpm


This blog listed the manufacturing years of the Duramax engine which should be avoided if you are planning to buy any vehicle powered by the Duramax engine. Duramax engines are used in Chevrolet and GM pickup trucks and cars, overall the reliability is good if the engines are serviced regularly.