How Many Miles Is a Duramax Good For? (Buying With 250k Miles)

It is hard to tell with some used engines how long they will remain functioning. However, diesel engines seem to get better with age, and a used diesel engine, like the Duramax can continue working for many years to come.

The exact figures may not be known as some Duramax engines last longer than others. The upper limit has been placed at around 250,000+ miles under proper maintenance. How long this engine lasts for you depends on how well you take care of it.

To learn more about the longevity of the Duramax engine, just continue to read our article. It has the information you want to know about so you have a good idea of how long the used model will continue to run without extensive overhauling.

What is The Duramax Engine?


Not everyone may have heard of this engine. It seems that the production of this model and brand was a joint venture between two famous auto makers. Those automakers are GM and Isuzu and they produced the engine for at least 16 years, at least that was when the 2,000,000 Duramax was made.

The engine is part of a family of 6.6 liter diesel engines produced by these companies. It was a V8 design that came in a variety of models over the years. It was also placed in different vehicles like the Hummer, Chevy, and GMC trucks from pick ups to medium-duty models.

The motor, depending on the model and year could put out between 300 and 400 HP with between 460 and 765 ft lb of torque, both at 3450 RPM. It is a powerful motor that has served both GM and Chevy well.

Over the years there were 8 renditions of this engine and all the renditions started with the letter L. There was the LB7, LLY, LBZ, LMM, LGH. LML, L5P, and the L5D.

Each model had its unique specifications with some overlap between them. Smaller motors in this family were also made and their displacement ranged between 2.5 and 3.0 Liters.

How Many Miles is a Duramax Good For?

Some owners may have been mistaken in their estimate of 250,000+ miles. It seems that the 6.6 Duramax has a lifespan of around 2,000,000 miles. With some estimates lowering that benchmark to 1,000,000.

With proper maintenance, it is said that the engine could last as long as 4,000,000. That extensive lifetime may be the exception and not the rule. Of course, the lifetime and mileage you get will vary.

Some engines are known to last a very long time while others do not make it too far past that 250,000+ suggestion. It is also said, that you can go that 2,000,000 miles without needing any extensive repairs or overhaul.

It seems that both GM and Isuzu used the 6.6 Duramax to solve some issues that were found in earlier engine models. The companies were able to fix faulty injection pumps and emissions systems that plagued other engine models prior to 2001.

Your driving habits, and how much you tow or haul will also play a large role in how long your 6.6 Duramax will last. If you do not tow or haul heavy loads, then expect it to last well beyond 2,000,000 miles.

How Long Will a LLY Duramax Last?


You know the figures and you know what you need to do to get this engine to last forever. If you do not do your end of the work, then do not expect to reach 2,000,000 let alone 1,000,000.

Even if those are inflated numbers, you can still have this engine last for as long as you own your vehicle and not do any major repairs. Even 500,000 miles is a good marker to reach.

But your mileage will depend on your regular maintenance program, the roads you travel, hauling or towing weight as well as if they are city or highway miles. There will be other factors involved, for example, if a part failed or you happened to have bought the weakest engine to come off the assembly line.

It is possible that your engine may not even make it past the 250,000-mile mark because of those failures. The best thing to say is that going over 1,000,000 miles is the dream or the ideal to shoot for.

There is just no guarantee that the engine will last as long as anyone says or claims. You just have to do your part to help it reach those high mileage figures.

Buying a Duramax With 250k Miles

Even though GM advertised the lifespan of this motor at 250,000 miles, buying one that has made it this far is not a problem. It may need extensive work done and it may not. That situation will depend on how well the previous owner took care of it.

Some people are leery about buying one of these motors at 150,000 miles as they said the parts are worn out by this time. That is one person’s opinion and not fact. There are many other opinions that counter that one.

We are aware of the lifespan between the two sources and to be realistic, it may be wise to accept the 250,000+ marker over the multi-million mile markers we reported earlier.

Some owners have reported their 6.6 Duramax has gone 440,000 miles without a major problem so the million-mile estimate is not too far off the mark. The key to buying and using an engine with 250,000 miles on it will be better maintenance.

You will have to take care of the engine to get it to last a lot longer than that mileage reading. The thing you need to consider is that the individual parts may not take the stress and pressure and may fail at any given time.

There is no way to gauge what will and when it will happen. It is a gamble when you buy a used engine with high mileage on it.

Buying a Duramax With 300k


This section will start with what ended the last section. Buying used is always a gamble no matter what you buy. You have no way of knowing what the engine went through prior to your purchase except for the owner’s word.

If you are looking at buying a Duramax with this many miles on it, then check it out thoroughly as you can. Ask for maintenance records or receipts for parts purchases and make sure you know what you are getting into.

300,000 miles on a Duramax is getting git close to when you may need to do extensive work or an overhaul on the motor. As you already know, buying used means you are buying someone else’s problems.

The engine could survive another 200,000 miles or it may break down in the first 1000 miles after your purchase. It is all a gamble when buying used. All the V8 6.6 Duramax engines came with the following components:

- These are V8 engines with OHV head construction and 4 valves per cylinder;

- All engines are turbocharged and they all have intercoolers to improve efficiency;

- They all have one of the best diesel injection - common rail types;

- They all have cast-iron blocks and aluminum heads, they are pretty repairable;

- The power is between 250 and 400 horsepower depending on the version;

- The peak torque may be up to 765 lb-ft and even more after some tuning. (source)

Thus all the 6.6 Duramax V8s should last a very long time under good treatment. Your driving habits may wear down some parts so do not be disappointed if you do not reach much higher than 300,000 miles.

Can a Duramax Go a Million Miles?

The one source we used for one section above made claims of 1,000,000, 2,000,000, and 4,000,000, and this mileage may have been reached by rare exceptions. We cannot verify those numbers as most other sources give a lot lower figure before the V8 6.6 Duramax needs work or dies.

According to a Duramax discussion forum, the highest figures reported were 500,000 and 550,000 with the engines still going strong after some repairs. They are also saying that those trucks, etc., getting these high mileage figures were and are stock.

Nothing was added to them so if you get a truck with this engine inside, do not do anything to it. For the most part, the mileage reports on that forum are around 200,000 to 300,000 and still going strong.

As we have said many times when we write about engines, sometimes you can get a lemon. One owner did and his blew at 10,000 miles. But he did not give up on this motor and bought a vehicle with a 6.6 Duramax under the hood. It has reached 500,000 miles and still going.

That forum thread runs for 14 pages and 265 posts so there may be other figures reported. Suffice it to say that if you take care of the engine, it will last a lot longer than 250,000 miles.

The answer to the question, after all of that, is whether it is possible this motor can reach 1,000,000 whether it does or not remains to be seen and verifiable. One point of interest to comment on.

The Duramax family of engines includes the 4 and 6-cylinder models that are the most recent renditions of this top tough engine. It is said that these are not the same engines as the 6.6 V8 and will not even see 300,000 miles.

There may be exceptions to this rule as well but that remains to be seen also.

LLY Duramax Turbo Inlet Manifold


These are still available and seem to be on sale at different outlets that sell diesel products. Those products can be parts or fluids, etc. The price at one outlet is $195 and that may be in Canadian dollars.

There are some customizers out there that may charge more for this part. That is understandable as there is a lot of work involved in making a new manifold. If you do a lot of shopping on the Internet, there should be a variety of outlets ready to meet your needs.

If you are in somewhat of a hurry, you can always check the junk or salvage yards. They may have what you need in stock and possibly for a lower price than you will find online.

What To Look For When Buying a High Mileage 6.6 Duramax

1. Look at condition- this is a double-edged sword as a dirty engine may tell you there are a lot of leaks and a super clean engine will tell you the owner is hiding those leaks.

Check underneath the engine for any fluids hitting the concrete or ground.

2. Check the engine’s history- this can be done through the VIN number or by going to Carfax to get a report on the engine. You can also ask for a maintenance record or receipts for parts bought by the owner.

3. Look at the exhaust pipe- a dying 6.6 Duramax will put out a lot of smoke when idling. Have someone push the gas pedal down and if you see a lot of black smoke, avoid buying this vehicle.

4. Listen to the engine- a good engine will run smoothly and there will be no rattling, vibration, or uneven work that will require lots of money to repair.

5. Don’t forget to test drive the vehicle- a sluggish feeling is a sign of a dying engine.

Some Additional Words

Unfortunately, the 6.6 Duramax V8 may not be in production anymore. It was and is a good engine that could last you a long time. The newer smaller versions are just not the same and you may not see the longevity out of them like you would the 6.6

Buying a used 6.6 Duramax may be better than buying a new smaller version of this tough engine.

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