Diesel-powered engines are famous for their reliability and efficiency, and as such, they are one of the most versatile workhorses in the industry. Diesel engines can offer excellent fuel economy, from the larger engines found in heavy-duty trucks to the smaller units in compact cars and everything in between. For those of you who need more than just the “best” in diesel efficiency, you’ve found it.
In this post, we delve into five of the most fuel-efficient diesel engines to date and how they’ve set the standard in both technology and practical application. You’ll also find out how these feats of engineering have affected the automotive world. And, you will leave here with some ideas to grasp how today’s state-of-the-art advancements, such as the now legendary 6.7 Powerstroke, fit into diesel’s larger ongoing story.
Why Fuel Efficiency Matters in Diesel Engines
Gas pump savings aside, fuel efficiency is not only a cost saver but also an element of sustainability and minor environmental impacts. It assists with the economy and reduces emissions, which is ideal in today’s powertrain eco-push. The engines listed here hit that sweet spot, delivering power without emptying your fuel budget or soiling the earth.
The featured engines were selected based on three key criteria:
- Fuel Economy: Impactful miles-per-gallon ratings or fuel-consumption ratios.
- Longevity: Durability and performance consistency over time.
- Versatility: Applicability across different vehicle categories and use cases.
1. Mercedes-Benz OM616 I4 / OM617 I5
The OM616 (4-cylinder) and OM617 (5-cylinder) engines are some of the most reliable and efficient diesel engines in the world. Manufactured from the early 1970s through the early 1980s, these engines established the benchmark for diesel efficiency at the time.
Specifications
- Fuel Economy: Up to 30 miles per gallon (depending on the vehicle).
- Power Output: Approximately 65–90 horsepower, depending on the displacement and variant.
- Applications: Commonly found in Mercedes-Benz models such as the 240D, 300D, and 300TD.
Why It’s Fuel-Efficient
These engines have a simple, naturally aspirated system, providing fuel efficiency and ease of maintenance. Forty years later, they power countless vehicles around the globe just through the sheer ruggedness of the thing and the excellent fuel economy.
2. Mercedes-Benz OM601 I4 / OM602 I5 / OM603 I6
Following the OM616 and OM617 inline fours, the I-5 and I-6 OM61x and the OM60x were updated to more modern diesels in the early 1980s up to the early 1990s. These motors were a step ahead in fuel economy and smoothness.
Specifications
- Fuel Economy: Around 26–34 miles per gallon in passenger vehicles.
- Power Output: Varies from 70–150 horsepower depending on the displacement and turbo options.
- Applications: Found in models like the Mercedes-Benz 190D, W124 series, and E300 Diesel.
Why It’s Fuel-Efficient
The new engines featured stripper fuel injection, a speeding device for increasing fuel combustion efficiency, and other technical innovations. Durable aluminum makes them lightweight, great for everyday use.
3. International Navistar T444E (7.3L Ford Power Stroke V8)
A list of good diesel engines wouldn’t be complete without the T444E/7.3 Power Stroke. This iron giant set a new benchmark for medium- and heavy-duty diesel engines.
Specifications
- Fuel Economy: Approximately 13–20 miles per gallon for trucks.
- Power Output: 210–275 horsepower.
- Applications: Most famously found in Ford Super Duty trucks (1994–2003).
Why It’s Fuel-Efficient
This motor is known for its straight injection system (HEUI), which makes it possible to control diesel better even when the demand is high. A mix of fuel efficiency, power, and reliability has made it popular in fleet applications and for truckers who spend a lot of time on the road.
4. Chevrolet HD 6.6L Duramax LB7 / LBZ (V8)
Chevy’s Duramax Diesel series, led by the 6.6L LB7/LBZ model, gave new meaning to what a diesel engine could be in terms of power and energy. Those engines have been around since the beginning of the 2000s, and are praised for their power output along with low fuel consumption.
Specifications
- Fuel Economy: Around 15–22 miles per gallon for pickups.
- Power Output: 300–360 horsepower.
- Applications: Found primarily in Chevrolet Silverado HD trucks and the GMC Sierra HD lineup.
Why It’s Fuel-Efficient
The LB7 was noteworthy for its common-rail fuel injection system, which required much higher fuel pressures to atomize the fuel better and for better combustion. Later, the LBZ modified it somewhat with added cooling capacity and programming targeted more towards fuel economy when used with a load.
Bonus Note
To streamline operations, many industries purchase supplies, including construction and logistics, sourcing PLG supplies. Engines like the Duramax LBZ, for example, are built to emulate the same durability and performance-geared standards highly regarded in these industries.
5. Toyota 1HD-FTE 4.2L I6
These are beloved engines among off-roaders the world over, praised for their power and reliability. First produced in the 90s and officially discontinued in the early 2000s, this inline-six is the perfect engine for off-roaders and overlanders.
Specifications
- Fuel Economy: Up to 25 miles per gallon.
- Power Output: 200+ horsepower.
- Applications: Primarily found in the Toyota Land Cruiser 100 Series and some Lexus SUV models.
Why It’s Fuel-Efficient
The combination of electronic direct injection and turbocharger control provides excellent fuel economy and impressive power. It’s long-lasting, too, which means its value for owners comes from lots of miles with very little wear and tear.
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Modern Impacts of Diesel Efficiency
The following five engines are indicative of how powerful a difference a powerful diesel engine can make in terms of savings on fuel, maintenance, and the environment. They also illustrate the innovation that makes diesel technology viable in today’s automotive environment.
What does this mean for the future? Pushing on for even greater efficiency and reduced emissions will only further change diesel technology. Whether driving the venerable 6.7 Powerstroke or dabbling in up-to-date offerings, the legacies of these landmark engines are helping dictate the direction of automotive engineering today.
