Cummins Vs. Duramax: Which Diesel Engine Has A Higher Life Expectancy?

Truck owners have an important decision to make when they're buying a new or used truck, what type of engine is best for them? The choice between a diesel engine and a gasoline-powered engine really comes down to what you require from your new truck. Two of the biggest diesel engine manufacturers are Duramax and Cummins, who make engines for General Motors and Stellantis, respectively.

Cummins began making engines in Columbus, Indiana in 1919 after Clessie Cummins, the then President of what was referred to as the Cummins Engine Company, developed the first Cummins engine. Since then, the company has gone on to develop a number of diesel engines, including the Model H engine, which was used for over 70 years.

The history of Duramax diesel engines is slightly less storied than its rivals. General Motors and Japanese manufacturer Isuzu teamed up to create a high-pressure direct-injection diesel engine for the U.S. market. In 1998, the two groups created DMAX Ltd., and in 2001 the LB7 Duramax diesel engine debuted. When comparing these two diesel engine manufacturers, a major question that arises is which of the two engines offers better life expectancy? Diesel trucks can easily surpass the 100,000-mile mark if they're maintained properly, and some continue chugging well passed 300,000 miles.

A properly maintained Duramax diesel engine can continue living even after surpassing the 300,000-mile mark. One of the most durable diesel engines ever created, the LB7 6.6L Duramax that the brand currently produces has been on the market since 2001. The LB7 Duramax features lightweight aluminum alloy cylinder heads when it debuted, something other brands didn't implement until the 2010s. In general, diesel engines are more reliable and will last longer than gasoline engines, this is because diesel engines are actually built to take on the higher compression ratios with much stronger materials. The stronger materials help the LB7 Duramax to continue to power large vehicles well past what a gasoline engine can offer.

A well-maintained LB7 Duramax that sees regular oil changes should be able to power a vehicle for 200,000 to 300,000 miles with relative ease. Unfortunately, when the LB7 surpasses the 200,000-mile mark, critical issues like the fuel system and timing components can become more at risk. There are owners who have laughed at 300,000-mile, pushing their Duramax-powered trucks past the 1,000,000-mile mark, a feat unheard of when it comes to gasoline engines. A man named Roger Hummel and his 2006 Chevy 2500HD were able to reach the million-mile mark in 2024, making sure to routinely change his oil every 25,000 miles.

Similar to the Duramax, a Cummins diesel engine that's been properly maintained can continue being used even after surpassing 300,000-miles. The standard Cummins engine you'll find in Ram pickups is the 6.7-liter Cummins that was introduced in 2007. That engine replaced Cummins' previous 5.9-liter engine, which had been powering Ram and Dodge trucks since 1989.

The previous Cummins 5.9-liter engine could easily surpass 600,000 miles. Though the newer 6.7-liter diesel is said to have an even longer life expectancy. With proper maintenance over the course of the engine's life and getting oil changes on time, it's not uncommon for Cummins engines to reach over 300,000 miles. In fact, Cummins even features a High Mileage Club that currently has more than 20,000 members.

The current High Mileage Club at Cummins is for any owner of a "Cummins-powered Ram, TITAN XD pickup, Cummins Repowered crate engine vehicle, RV, or other Cummins powered vehicle has surpassed the 100,000-mile mark." Cummins offers members a die-cast Cummins grille badge to commemorate the achievement. Beyond that, the brand also features a Million Mile Club, though the number of members remains a mystery.