How Long Will a LLY Duramax Last, and Is It a Reliable Engine?

Whether you own a Duramax LLY before or after you buy one, the first thing you’ll want to know is how long it’ll last.

How well the maintenance is done determines how long it lasts.

Maintaining your Duramax LLY well will extend its lifespan many miles beyond its average lifespan.

What Year Duramax is LLY?

In 2004, LLY Duramax V8 engines were introduced.

It is a 6.6L Duramax V8 engine that replaced the LB7 Duramax V8 engine.

There are a bunch of Chevrolet and GMC vehicles with this engine, including:

  • Chevrolet Silverado HD [2004-2005]
  • GMC Sierra HD [2004-2005]
  • Chevrolet Silverado HD [2006]
  • GMC Sierra HD [2006]

The 6.6L LLY Duramax V8 produced up to 310 hp (232 kW) at 3000 RPM and torque around 520-605 lb.-ft (705-820 Nm) at 1600 to 1800 RPM.

How Long Will a LLY Duramax Last?

The Duramax LLY engine lasts for around 200000 miles or 321869 kilometers without needing any major maintenance or repairs.

It has a 95% GM user rating.

It means 95% of Duramax LLY engines last over 200000 miles without any major issues.

However, the lifespan of an LLY Duramax depends on the maintenance of the engine as well as the vehicle.

With proper maintenance, you can easily cover more than 500000 miles (804672 kilometers) with a Duramax LLY engine.

Maintenance is the key to the longer lifespan of a Duramax LLY.

So, you must know how to maintain your Duramax LLY.

I am giving you 8 maintenance tips that will help to enhance the lifespan and engine performance of your Duramax LLY.

08 Maintenance Tips for Duramax LLY

  1. Change engine oil and oil filter every 10000 miles (16094 km).
  2. Change the fuel filter every 15000 miles (24140 km).
  3. Replace the air filter every 35000-45000 miles.
  4. Always check the cooling system.
  5. Check leakages regularly.
  6. Never ignore the check engine light.
  7. Replace auto transmission fluid every 50000 miles (80467 km).
  8. Replace engine glow plugs and wire every 60000 miles (96561 km).

How Long Do LLY Injectors Last?

A well-maintained Duramax LLY injector lasts over 160,000 miles to 200,000 miles.

After this period, the injector usually gives the following 07 types of warning signs-

07 Injector Failure Symptoms

  1. Lack of power
  2. Misfires
  3. Rough idling
  4. Check engine light on
  5. Bad fuel economy
  6. Fuel smell
  7. Hard to start

You will face the following symptoms before 200,000 miles if you do not maintain the injector properly.

Price of Duramax LLY Injectors

You must change all 8 injectors of Duramax LLY to avoid the above symptoms.

It will cost you around $2500 to $3200, including the mechanic charges.

LLY Duramax MPG

6.6L Duramax LLY V8 engine provides 22 mpg on the highway and 16 mpg in the city.

Duramax LLY is a mid-level fuel-efficient engine.

However, GM has more advanced fuel-efficient engines these days.

LLY Duramax 0-60

6.6L Duramax LLY reaches 0-60 mph in just 5 sec.

Duramax LLY is a fast engine, and its maximum engine speed is 3000-3200 RPM.

Is the LLY Duramax a Good Engine?

The 6.6 LLY Duramax is known as the second-generation Duramax engine.

LLY is an updated version of LB7, and it doesn’t suffer from injector problems like LB7.

LLY (2004-2005) model has 5-speed Allison Transmission, which was updated to 6-speed Allison Transmission in the 2006 model.

LLY is a powerful, reliable engine.

A Duramax LLY engine can generate up to 310 horsepower at 3000 RPM, which is higher than any 2004 or 2005 engine available on the market.

Although LLY has these benefits, it has some minor problems.


How Many Miles Can You Get Out of a LLY Duramax?

You can expect 300,000 miles or more if you maintain it properly.

Changing engine oil, air filter, and fuel filter timely, and taking necessary steps when the engine check light appears, are included in proper maintenance.

Are LLY Duramax Reliable?

Duramax LLY is a very reliable engine.

It is free from the injector failure problem that LB7 has.

Compared to modern trucks, the LLY emits fewer emissions than modern trucks do.

Is the LLY Duramax a Good Engine?

The LLY Duramax is a reliable mid-range engine.

It is a better-quality engine compared to the engines of its time.

It provides 310 horsepower and a substantial towing capacity of around 12,000 pounds.

How Long Do Duramax LLY Engines Last?

Duramax LLY was introduced in 2004 as a replacement for the Duramax LB7 engine.

It overcame the shortcomings of the LB7 engine.

But the lifespan of LLY and LB7 is almost identical, and it is 300,000 miles.

Final Thoughts

Duramax LLY is the successor to Duramax LB7.

LLY was introduced in 2004.

It was a very reliable engine with a long lifespan for its time. But the key is maintenance.

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