Diesel Engines in America: A Brief Overview
While diesel engines have become synonymous with reliability and efficiency in many parts of the world, particularly in Europe, they have not achieved the same level of popularity in American passenger cars. This disparity is largely attributed to strict emissions regulations and a market preference for gasoline engines. The turning point for diesel acceptance in the U.S. came with the infamous 2015 Volkswagen Dieselgate scandal, which severely damaged public trust in diesel technology. Today, diesel engines are predominantly utilized in heavy-duty trucks and commercial vehicles, where they excel in torque and fuel efficiency.
For example, models like the Ford 6.7L Power Stroke are renowned for their impressive torque ratings, making them perfect for towing and hauling while also offering commendable fuel economy for long-distance travel and work-related applications. Compiling a definitive list of the most reliable diesel engines is a complex task due to numerous influencing factors, including owner maintenance practices, climate conditions, and specific applications. The following list draws on data from RepairPal and CarComplaints, acknowledging that even engines with minor, recurring issues can still demonstrate remarkable durability when subjected to proper maintenance.
Despite the various reliability metrics, each engine featured here has earned a reputation for long-term dependability, particularly when proactive care is applied. No engine listed can be deemed a failure; all are celebrated for their ability to log high mileage and deliver consistent performance, even if certain components or emissions systems may require occasional attention.
Table of Contents
- 1. BMW M57 3.0L I6: Performance Meets Longevity
- 2. Volvo D5 2.4L I5: Scandinavian Toughness
- 3. VW Group EA827 TDI: Economical and Enduring
- 4. Ram HD Cummins ISB: Legendary Inline Six
- 5. Ford 6.7L Power Stroke V8: Modern Muscle
- 6. Toyota 1HD-FTE 4.2L I6: Built for Endurance
- 7. Chevrolet Duramax LB7/LBZ V8: GM’s Diesel Workhorse
- 8. Ford 7.3L Power Stroke V8 (T444E): Old-School Reliability
- 9. Mercedes OM60x Family: Million-Mile Machines
- 10. Mercedes OM616/OM617: Diesel’s Gold Standard
1. BMW M57 3.0L I6: Performance Meets Longevity
The BMW M57 3.0L diesel engine has set a standard for performance and durability in a range of models, including the 3, 5, and 7 Series as well as SUVs like the X5. This engine is celebrated for its smooth power delivery and robust internal components, often lasting hundreds of thousands of miles. However, owners should be aware that emissions-related components—especially the EGR, DPF, and turbo seals—often require maintenance or replacement over time. Issues such as crank damper failures and cooling system leaks can arise, yet the main components of the engine remain steadfast when routine care is performed. Regular highway driving can significantly reduce emissions-related problems, ultimately extending the life of the engine for dedicated BMW diesel fans.
2. Volvo D5 2.4L I5: Scandinavian Toughness
Volvo’s D5 engine, designed on its modular gas engine architecture, is an inline-five diesel used in vehicles like the S60 and XC90. Known for its robust aluminum block and iron liners, this engine is engineered to withstand the intense pressures of diesel combustion. Praised for its smooth operation and torque output, the D5 frequently surpasses 200,000 miles, with even higher mileage achievable through diligent maintenance. Key concerns include cooling fan failures, fuel line leaks, and timing belt issues, the latter of which can lead to severe damage if not addressed. With proper care, including timely timing belt replacements, the D5 stands out as one of the more resilient European diesel engines available in the U.S. market.
3. VW Group EA827 TDI: Economical and Enduring
The VW Group’s 1.9 and 2.0 TDI engines are among the most iconic diesel units in the U.S., despite the lingering shadow of Dieselgate. Renowned for their exceptional fuel efficiency and solid engineering, these engines have powered millions of models, including Golfs, Jettas, and Audis. The 1.9L variant is particularly notable for its longevity, albeit with a reputation for noise, while the 2.0L version offers a more refined experience. Regular timing belt changes are crucial, and owners should remain vigilant about potential EGR issues and dual-mass flywheel failures. With consistent maintenance, these TDIs can easily surpass 300,000 miles, providing economical operation without compromising reliability.
4. Ram HD Cummins ISB: Legendary Inline Six
The Cummins ISB engine, particularly in its 5.9L and 6.7L variants, is a legendary powerhouse in the diesel truck community. Found in Ram HD trucks, this inline-six engine is known for its immense torque and remarkable reliability. Since its inception in the 1980s, the engine has evolved with advancements like 24-valve heads and common-rail injection technology. While issues such as VP44 pump failures or turbo vane sticking can occur—especially in earlier models—the core engine remains nearly indestructible. With appropriate servicing and attention to emissions components, these engines are known to easily exceed 350,000 miles, making them a top choice for heavy-duty applications due to their simplicity and durability.
5. Ford 6.7L Power Stroke V8: Modern Muscle
Ford’s 6.7L Power Stroke engine, developed internally and introduced in 2011, marked a significant advancement in diesel engine design for the brand. Used in F-250 and F-350 Super Duty trucks, it delivers an impressive torque output of up to 1,200 lb-ft. Initial issues, such as failing ceramic ball-bearing turbos and weak Bosch CP4.2 fuel pumps, were effectively addressed by 2015. Subsequent models showcased enhanced reliability, featuring robust head gaskets and improved EGR systems. This engine thrives on regular maintenance, and with consistent oil changes and cooling system inspections, it is well-equipped to reach the 400,000-mile mark, making it ideal for demanding power applications.
6. Toyota 1HD-FTE 4.2L I6: Built for Endurance
The Toyota 1HD-FTE engine, a straight-six turbodiesel found in Land Cruisers and Hilux models, has garnered global acclaim for its reliability and ruggedness. Although not commonly available in the U.S., imported models have cultivated a dedicated following. These engines routinely achieve half a million miles, with essential maintenance tasks including timing belt replacements and EGR cleaning. Valve clearance checks every 40,000 miles are also recommended. The simplicity of its mechanical fuel system contributes to its reputation for durability, making it a favorite among off-road and expedition enthusiasts who rely on its performance under extreme conditions and excellent low-end torque.
7. Chevrolet Duramax LB7/LBZ V8: GM’s Diesel Workhorse
The Chevrolet LB7 and LBZ 6.6L Duramax engines, developed in collaboration with Isuzu, marked GM’s significant entry into the modern diesel engine arena. Featured in Silverado and Sierra HD trucks, the LB7 introduced common-rail injection and aluminum heads, while the LBZ boasted stronger internals and fewer emissions constraints. While the early LB7 models experienced injector and fuel filter housing issues, these were resolved in later iterations. Both engines are celebrated for their durability and smooth operation, with many trucks reaching 500,000 miles or more. Their combination of performance, simplicity, and extensive aftermarket support makes them highly regarded among diesel truck enthusiasts and heavy-duty operators alike.
8. Ford 7.3L Power Stroke V8 (T444E): Old-School Reliability
The 7.3L Power Stroke, derived from International Navistar’s T444E design, is often lauded as one of the most trusted diesel engines ever produced. Installed in Ford Super Duty trucks from 1994 to 2004, it utilized Hydraulic Electronic Unit Injector (HEUI) technology and forged internals, resulting in unmatched strength. Known for its ability to surpass 500,000 miles—especially in post-1997 models—it has garnered a passionate following. Its all-iron construction and hydraulic lifters contribute to its durability and low maintenance needs. Issues such as CPS sensor failures or up-pipe leaks are manageable and well-documented, further establishing the engine’s reputation as a diesel legend in the truck community.
9. Mercedes OM60x Family: Million-Mile Machines
The Mercedes-Benz OM601, OM602, and OM603 engine family epitomizes diesel longevity and reliability. Used from the early 1980s until 2000, these engines powered models such as the W124 and were available in inline-4, -5, and -6 configurations. Renowned for their smooth operation and high-mileage capabilities, many units have surpassed one million miles. The modular design simplifies maintenance, although early OM603 variants faced challenges such as cracked heads and bent rods. Nevertheless, these engines are revered for their indestructible architecture and minimal maintenance requirements, often found in enthusiast-owned W124s and older Mercedes sedans still operating decades after their original production.
10. Mercedes OM616/OM617: Diesel’s Gold Standard
The OM616 and OM617 engines are widely regarded as the most reliable diesel engines ever manufactured, powering numerous W123 and W116 Mercedes-Benz models from the 1970s and 1980s. Designed by the legendary Ferdinand Piëch, these naturally aspirated and turbocharged engines are known for their ability to exceed one million miles, with some taxis reportedly surpassing 4.3 million miles in service. While producing modest horsepower, these engines emphasize durability and ease of maintenance. Routine oil changes, valve adjustments, and fuel system upkeep are sufficient to keep them running for an extended period. Although these engines are now considered old, their simplicity, over-engineered design, and availability of parts ensure they remain on the road and are celebrated among diesel purists.