Life Expectancy: How Long Do Cummins Engines Last?

If you are buying a new heavy duty truck that you will test with the demands of daily use, you have likely considered a Cummins engine. After all, approximately 75% of all Ram 2500 and 3500 pickup owners go with the optional Cummins Turbo Diesel, knowing that it is one of the most well-regarded engines for heavy-duty use.

But when you're investing in something important, you need to be able to answer a straightforward question: how long do Cummins engines last?

The answer to this question is not as clear. The life expectancy of a Cummins engine can vary widely based on how it is used and maintained and the environment in which it operates.

Below, we'll examine the specifications of the 5.9 and 6.7 models, the proper maintenance they will need, and the high mileage you can expect if everything is done correctly.

What is a Cummins Engine?

Cummins has been an industry leader for more than 100 years, one of the world's most popular engine manufacturers. The company is known for its innovative designs, superior quality, and excellent durability.

If you are looking for a reliable engine that will outlast its competitors, especially when it comes to complex jobs, you're usually looking for a Cummins. For pickups, the two main engines discussed are:

• 5.9L: Introduced in the 1989 Dodge model, this behemoth revolutionized the pickup industry by providing the power and reliability that had previously only been seen in much larger vehicles.

• 6.7L: In response to increasing emissions standards, Cummins released the 6.7 in 2007 as an upgrade to the 5.9 model.

Both of these engines are well-regarded for their performance and longevity but have different profiles regarding high mileage and maintenance.

Diesel vs. Gas Engine Life Expectancy

How are diesel engines able to get superior mileage? One of the main reasons is that they run on diesel fuel, which flows better inside cylinders to create a more efficient combustion process.

Gasoline acts more like a solvent than oil and will eventually wear down the lubricant used to prevent pistons from rubbing against each other. That causes engine parts to wear down faster than those operating with diesel.

The biggest separators between diesel vehicles and gasoline-powered vehicles are:

• Fuel efficiency: Diesel offers better fuel economy, burning about 15% less than gasoline

• Lifespan: Diesel engines can last much longer than gas engines because of the lubricating properties of diesel fuel

• Power: Diesel engines generate more torque and horsepower than their gasoline counterparts, allowing for more towing and hauling capacity

• Emissions: Gasoline burns more cleanly than diesel, but modern diesel engines are catching up with advanced emission controls

• Cost: Diesel engines are more expensive to buy than gasoline, but the cost of ownership over time can end up resulting in a higher return on investment thanks to its long lifespan

For heavy-duty usage, there is no question that a diesel engine is the way to go.

What Makes Cummins Engines so Effective?

The story of the 5.9 begins in agriculture and construction, which is part of why it has been so successful in pickup applications.

With a design that originally focused on the most demanding applications, when applied to Dodge pickup trucks a few years later, it brought with it all the toughness and reliability that had already made it so successful in other vehicles.

The 6.7 Cummins reliability has been similarly lauded. Still, the most significant change was the new emission control system that allowed Cummins to meet 2007 EPA standards without sacrificing power or fuel economy.

The turbocharger technology compresses air from the intakes for increased power output while connecting the camshaft to the crankshafts allows for better control of fuel injector timing.

Additionally, both models have a strong aftermarket support network with plenty of options for upgrades, repairs, and maintenance - making it easy to keep your engine running at peak performance.

How long does a diesel engine last?

Consumer Reports found that the average Cummins diesel motor can last up to 300,000 miles, though that number can vary wildly based on how it is used and maintained. A neglected engine will give out sooner than one regularly serviced and kept in good condition.

5.9 Cummins High Mileage

You might be surprised to learn that the 5.9 Cummins can easily last more than 600,000 miles with proper maintenance. The company is so confident in its reliable engines that they maintain a High Mileage Club with more than 20,000 members.

More than 110 of those have pushed the 5.9 to more than one million miles, showing how incredibly durable the beast can be.

Even in 2022, 15 years after they were discontinued, you can still find Cummins 5.9 diesel engines on the road, pulling heavy loads and taking on challenging jobs.

Cummins 6.7 Diesel High Mileage

In 2007, when the 6.7 was introduced, the focus was on meeting emissions standards. But even with extra torque at lower RPMs and more fuel efficiency, it still retained its predecessor's reliability and longevity.

The 6.7 Cummins has a longer expected life than the 5.9L, with many engines lasting up to 300,000 miles with proper maintenance.

But just like its predecessor, it can last much longer if well taken care of. The High Mileage Club already has a handful of 6.7L engines that have reached the 1 million mile mark, with thousands of others well on their way.

Maintenance of Cummins Engines

Like any other engine, regular maintenance is essential to the longevity of a Cummins.

• Quality parts: The age-old adage of ‘you get what you pay for’ also applies to Cummins engines. Invest in quality fuel filters, lubricants, and other engine components whenever possible.

• Regular oil changes: Regular engine oil changes are essential for a Cummins engine's proper performance and longevity. Change the oil at least once yearly or every 5,000 miles (whichever comes first).

• Coolant flushes: Coolant should be flushed at least once per year to remove contaminants and prevent corrosion from occurring in the cooling system.

• Engine debris: Check for any debris or build-up in the engine regularly. Check for debris and build-up can be done by removing the valve cover.

You can expect your Cummins engine to last for many years and miles with routine, comprehensive maintenance.

Frequently Asked Questions

What are the advantages of diesel engines?

The longevity of diesel-powered vehicles, which can sometimes run for more than one million miles, gives them a huge advantage over gasoline engines which are rarely able to compete in tests of durability.

What benefits can a diesel engine offer?

Diesel trucks provide several benefits, including increased fuel efficiency, better torque and power than gasoline engines, and longer life expectancy.

What makes a diesel engine last longer?

Because diesel fuel is a light oil, it lubricates the engine's components better than gasoline, which helps improve its lifespan. Diesel engines also usually run at lower RPMs and don't require spark plugs, adding to their longevity.

Why do diesel engines have better fuel economy?

Diesel engines are more efficient than gasoline engines because they use higher compression ratios, allowing them to extract more energy from a given fuel.

Final Thoughts

If you are looking for a long-lasting engine, Cummins should be at the top of your list. Following the proper maintenance schedule, you can expect your Cummins engine to last hundreds of thousands of miles with minimal issues.

Want to learn more? Check out the variety of Cummins engine parts offered by Heavy Duty Pros. We offer a wide range of quality replacement aftermarket parts for all industries.