It’s no secret that diesel engines aren’t nearly as popular in the U.S. as they are in Europe and other markets.
Diesel engines have long been favored across Europe, but their presence in the U.S. remains relatively limited. Several factors contribute to this, including GM’s infamous diesel missteps in the 1980s and lingering perceptions that diesel engines are noisy, smelly, and produce excessive nitrogen oxide emissions.
Despite this reputation, diesel engines are actually more fuel-efficient than gasoline engines, and advances in emissions technology have significantly reduced their environmental impact. Still, diesel-powered passenger vehicles remain rare on American roads.
That said, there’s one area where diesel thrives in the U.S.—work vehicles.
Heavy-duty applications such as semi-trucks, tractors, and commercial transport vehicles rely heavily on diesel engines. Their longevity, superior torque, and impressive fuel economy make them the go-to powertrain for moving heavy loads.
Many of the most iconic diesel engines ever produced have found their home in American work trucks and machinery, often running strong for hundreds of thousands of miles.
Navistar DT466
Among diesel engines, few have the legacy and respect of the Navistar DT466. Manufactured by International, this engine debuted in 1971 for agricultural use and was redesigned in 1975 for highway vehicles. Over its 45-year production run—ending in 2016—it found a home in trucks, buses, farm equipment, and even military vehicles.
One of the DT466’s standout features is its durability. With a B50 life expectancy of 550,000 miles, half of these engines are expected to last that long before requiring major repair—a remarkable achievement. Numerous revisions over the years, including a switch from mechanical to HEUI (Hydraulic Electronic Unit Injector) fuel injection and various emissions improvements, kept it modern.
Perhaps most notably, the DT466 featured a wet sleeve design, which simplified maintenance and extended engine life. This innovation helped cement its status as one of the most dependable diesel engines ever made.
Mack E7
Known for its presence in the semi-truck world, Mack has built a reputation around reliable engines—and the E7 is a key part of that legacy. Introduced in 1988, the E7 was offered in several configurations tailored to different industrial, agricultural, and commercial needs. By 1999, 16 different versions existed, and it remained in production for just over two decades.
Much like the DT466, the E7 gained a reputation for its toughness. Stories abound of trucks running well beyond a million miles, often under heavy loads. While mileage data is limited due to the E7’s use in stationary and off-road equipment, its widespread acclaim speaks for itself.
The E7 also delivered serious performance, with top models producing up to 454 horsepower and a staggering 1,660 lb-ft of torque—more than enough to handle demanding hauls.
Ford 6.7-liter Power Stroke Diesel
Still in production today, Ford’s 6.7-liter Power Stroke diesel engine represents a high point for the brand’s heavy-duty offerings. It replaced previous diesel attempts with an in-house design focused on power and reliability. In its current form, it delivers up to 450 horsepower and 1,050 lb-ft of torque.
This engine is commonly found in Ford’s Super Duty truck lineup—from the F-250 all the way to the F-750. When fully outfitted, the F-450 equipped with this engine can tow up to 40,000 pounds—roughly the weight of a small house.
Earlier models faced a few reliability issues, but Ford made improvements over time. Today’s 6.7-liter Power Stroke is a dependable choice for both commercial and personal use.
Navistar/Ford 7.3-liter Power Stroke
Before the 6.7-liter Power Stroke came the legendary 7.3-liter version, developed jointly by Ford and International (Navistar). This engine, launched in 1994 and based on the Navistar T444E, quickly earned a reputation for reliability and power.
Its success stemmed from its durability, ease of maintenance, and capacity for abuse. With 225 horsepower and 450 lb-ft of torque at launch, it outperformed its light-duty diesel peers and enabled towing capabilities exceeding 10,000 pounds.
Ford phased out the 7.3-liter in 2003, replacing it with less-celebrated 6.0- and 6.4-liter versions. Looking back, the 7.3-liter is often regarded as the pinnacle of the Ford-Navistar collaboration.
Cummins 4BT
The 3.9-liter Cummins 4BT diesel is known for its flexibility and resilience. First introduced in 1983, it found use in delivery trucks, industrial machines, buses, and even marine applications. The engine received a significant update in 1998, evolving into the 4BTA.
Though modest in output—170 horsepower and 420 lb-ft of torque for the 16-valve version—the 4BT’s real value lies in its adaptability. It’s a favorite among engine swappers due to its compact size and legendary dependability.
While detailed production data becomes murky after the early 2000s, the 4BT remains in use today through Cummins’ ReCon remanufactured engine program.
Cummins 6BT
Larger and more powerful than the 4BT, the 5.9-liter Cummins 6BT is a straight-six diesel powerhouse. Delivering up to 215 horsepower and 440 lb-ft of torque, the 6BT helped revive Dodge’s pickup truck line in the early 1990s.
This engine became a favorite for its strength, reliability, and mechanical simplicity. Though heavier and bulkier than the 4BT, it offered more performance and is still sought after today for both on- and off-road use.
Available in various versions, including the 6B, 6BT, and turbocharged 6BTA, the engine remains in production through Cummins’ ReCon program, now often marketed for marine applications.
Cummins ISB 6.7-liter
The Cummins ISB 6.7-liter is the modern successor to the 5.9-liter 6BT. Introduced in 2007, it brought with it a 13% increase in displacement, updated emissions systems, and advanced electronics.
Despite the new tech, it stayed true to the B-series reputation for durability. Known for hitting well over 300,000 miles, it’s used in everything from Ram heavy-duty trucks to commercial chassis and the Nissan Titan XD (2016–2019).
Producing 420 horsepower and up to 1,075 lb-ft of torque, the ISB 6.7-liter combines modern performance with old-school durability, making it one of today’s top diesel engines.
Duramax LB7 V8
The LB7 was the first engine developed through the GM-Isuzu partnership, debuting in 2001 and ending production in 2004. Though its run was brief, it’s widely considered one of the best Duramax engines ever built.
Performance was solid for its time, but its reliability was what really set it apart—once fuel injector issues (common around 100,000 miles) were addressed. Engines that made it past that mark often went on to reach 300,000 miles or more, with a few hitting the million-mile milestone.
The LB7 laid the foundation for future Duramax engines and helped solidify the GM-Isuzu relationship—at least until the partnership ended in 2016.
Duramax LBZ V8
Regarded by many as the best Duramax engine, the LBZ was built for just two years (2006–2007). It replaced the LLY, which struggled with reliability issues. With 360 horsepower and 650 lb-ft of torque, the LBZ offered robust performance and strong towing capabilities.
Despite its short production life, it earned widespread praise. Many examples have comfortably passed 200,000 or even 300,000 miles. Enthusiasts still seek out LBZ-equipped trucks for their power and dependability.
It was also one of the last diesels produced before emissions regulations introduced Ultra Low Sulfur Diesel in 2007. That regulation shift prompted GM to roll out the less-loved LMM engine, making the LBZ the last of a breed.