Last Updated on February 25, 2022
We set heavy expectations on the trucks we drive, and not just transportation or hauling. However, trucks can’t do half of what we want, not without a reliable, high-performance engine. That’s why for heavy-duty operations, truck manufacturers choose diesel engines.
If you are trying to decide which engine is better – diesel or gasoline – then we have the answer. Whether you are concerned about fuel efficiency, reliability, or any other quality, this article will point you in the right direction. No engine is made perfect, but some are definitely made better,
Keep reading to learn the top 3 best diesel engines for pickup trucks, and just what edge diesel engines offer over their gasoline counterparts.
Diesel versus Gasoline Engines
Diesel engines offer several advantages over gasoline engines. One of the most important distinctions is that diesel engines produce more torque, essential for towing. More torque equals more towing power This is why manufacturers equip trucks with this type of engine.
One example of increased torque is the Ford F-250, capable of towing up to 15,000 pounds when equipped with the gas V8 engine. On the contrary, the truck can tow 20,000 pounds when equipped with the 6.7-liter turbodiesel V8. The difference in torque capacity is undeniable.
Diesel engines also typically last longer than gas engines. This is true even under demanding towing conditions. For this reason, fleet operators often choose vehicles equipped with diesel engines, which typically deliver 300,000 miles or more when properly maintained and used.
These engines last longer due to being composed of more durable parts.
Another benefit – diesel engines are more fuel efficient than the gasoline variety. In fact, they are 20-35 percent more efficient. Diesel engines don’t need to burn as much fuel as a gas engine to get the same level of power. Thus, they’re more efficient.
Here’s an example – the Ford F-150 comes equipped with a 3.0-liter turbodiesel. The truck with this engine achieves 24 miles per gallon (mpg), factoring in both city and highway driving. The same truck equipped with a turbocharged gas 3.5-liter V6 only gets 18 mpg. The difference then is a 33 percent difference in fuel efficiency. Better fuel efficiency also translates into less engine wear, so diesel engines last much longer than gasoline engines. They also don’t require tune ups, but the gasoline types do.
Both gasoline and diesel engines emit pollutants, but the latter releases cleaner gases from the tailpipe. Although, they also emit nitrous oxide (NOx), which causes smog.
When idling, diesel engines produce a large rattle, but run at about the same decibel as their gasoline counterparts.
While the differences between the engines is noteworthy, there are drawbacks. The financial savings created by this efficiency difference is countered by the higher price of diesel fuel. And when repairs are needed, diesel engines cost more than gasoline engines.
There is no surprise then that trucks equipped with diesel engines have a higher purchase cost than trucks equipped with gasoline engines.
History of the Diesel Engine
In the late 19th Century, while studying thermodynamics, Rudolf Diesel imagined a highly efficient engine that could convert the heat it generated into power. In 1985, he established a shop to test and produce that very concept.
Diesel received patents for his designs and built the first prototype engine in 1893. The prototype proved unsuccessful. After tweaking the engine, he produced a second generation model in 1897. This version demonstrated 16.2 percent efficiency compared to the steam engine, which was the most popular form of power for machines.
At the consumer level, Diesel’s engines proved unreliable, which led to returns and refunds. However, militaries saw potential in diesel-powered machines because the fuel was less likely to explode. By 1904, France started using diesel engines in their submarines. Other militaries eventually used diesel to power boats, trains and trucks.
In 1908, Diesel’s patent expired. This was the same year the first diesel-powered truck came onto the market.
Diesel in the 20th Century
Almost all pick-up trucks produced in the 20th Century were powered by gasoline engines. Then manufacturers started considering the potential of diesel engines for increasing hauling and towing capacity of their trucks. Then in 1982, Ford and GM introduced diesel-powered trucks.
Ford began producing diesel engines in partnership with International Truck and Engine Corporation (ITEC). They produced a 6.9-liter indirect injection (IDI) diesel engine, which offered 170 horsepower (hp) and 315 pound-feet (lb-ft) of torque. Production of the 6.9-liter IDI engine continued until 1987. In this year, Ford introduced a 7.3-liter IDI engine named the Powerstroke.
Although GM already had a 5.7-liter diesel engine, they decided to work with Detroit Diesel to introduce consumer light-duty trucks. These trucks came equipped with a Detroit Diesel 6.2-liter engine. They produced 130 horsepower and 240 lb-ft of torque, while achieving about 20 mpg.
In 1989, Dodge introduced their first diesel-powered Ram truck. The truck came equipped with the Cummins B-series engine. Cummins had been a leader in the commercial truck market and the B-series engines marked the company’s first foray into the medium-duty pickup truck market. Their first engine offered only 160 horsepower, but also offered 400 lb-ft of torque, which surpassed the competition.
Some years later, Ford redeveloped their diesel engine and in 1994 released their first trucks with a Powerstroke turbo-diesel direct-injection engine. That same engine technology powers their larger trucks today. They announced a second generation in 1999, which is heralded by some as the best engine ever produced.
Diesel in the 21st Century
Meanwhile, Cummins boosted their engine above 200 horsepower in 1996 and surpassed 500 lb-ft of torque in 2001.
In the late 90’s, GM lagged the competition in the diesel pickup truck market with about a three percent market share. GM dropped Detroit Diesel and started working with Isuzu. The company Isuzu had been working on a new diesel engine design, which was scheduled for release in 2003. However, the company created a 60/40 joint venture with GM to create a new company called DMAX, who would produce the new engines two years ahead of schedule.
The new engines were called Duramax in order to market the engine’s durability and maximum power characteristics. These engines first appeared on 2001 models.
Capable of offering 235 horsepower and 500 lb-ft of torque, the 6.6-liter Duramax Diesel 6600 easily made a splash. In the year 2000, Popular Science Magazine awarded it with the “Best of What’s New Award”. Ward’s Magazine chose it as one of the “Ten Best Engines in the World” in 2001 and again in 2002. The engine was instrumental to Motor Trend Magazine who chose the 2001 Chevrolet Silverado Heavy Duty pickup truck for its “2001 Truck of the Year Award”.
Engines across the three major manufacturers increased in horsepower and torque output while creating new technologies and strategies for meeting evolving and ever stricter environmental standards.
What Is the Best Diesel Engine?
Many consider the Duramax 6.6-liter (Chevy/GM), the Cummins 6.7-liter (Dodge) and the Powerstroke 6.7-liter as the best diesel engines available for 2021-2022 pickup trucks.
Criteria for deducing which engines are best include:
- Peak horsepower
- Peak torque (towing capacity)
- Fuel efficiency
Horsepower is a common criterion for comparing engines. People specifically focus on the peak horsepower. Peak horsepower occurs only when the engine hits a certain number of revolutions per minute (rpm). Engines are designed to create and transmit power to the truck. Thus generally, more horsepower translates into faster pick up speeds and faster top speeds.
Torque is another measure of power. Torque is the power needed to move a truck from a standstill into motion and to haul heavy loads. As mentioned earlier, torque is measured in pound-feet or lb-ft for short.
The Duramax 6.6-liter diesel engine features 360 horsepower at 3,200 rpm, and 650 lb-ft of torque at 1,600 rpm. The Cummins 6.7-liter features 385 horsepower at 2,800 rpm, and 865 lb-ft of torque at 1,700 rpm. And the Powerstroke features 275 horsepower at 2,800 rpm, and 525 lb-ft at 1,600 rpm.
Remember – fuel efficiency saves on fuel costs, but is also more expensive than gasoline. Fuel efficiency is also dependent on a number of other factors with your truck. If you put an engine in a truck with a crew cab, extended bed, and other similar options, your truck will be less fuel efficient.
One way to make such a comparison is by comparing the base model of the Chevrolet Silverado 3500 (Duramax) with the Dodge Ram 3500 (Cummins) and the Ford 350 (Powerstroke).
The Silverado 3500 offers 17 mpg / 23 mpg / 19 mpg (city and highway combined). The Dodge Ram offers 13 mpg / 16 mpg / 15 mpg, and the Ford F-350 offers 9 mpg / 15 mpg / 11 mpg.
Reliability is an important part of being a great engine. Performance doesn’t matter when the engine is in the shop. All three of the aforementioned engines are reported to be reliable, but read on for greater details about potential problems.
Longevity is important because installing a new engine is costly. All three of these engines have been reported to last more than 300,000 miles. Predecessor engines to these models (ones that have been on the road for more than a decade) have been reported to last more than 500,000 miles.
Listing the Best Pickup Truck Diesel Engines
Duramax 6.6 turbo diesel V8
The Duramax 6.6L V8 turbo-diesel engine turned 20 this year and is in its sixth engine variation (called L5P). The latest generation, which was introduced in 2017, has nearly doubled its traits from 235 horsepower and 500 lb-ft of torque to 445 horsepower and 910 ft-lb of torque. All while decreasing exhaust emissions. Today, there are more than 1,000,000 Duramax engines on the road.
Duramax diesel engines generate a lot of energy and maintain great performance efficiency throughout your travel experience. In a GM Sierra 2500HD Crew Cab 4WD, it can accelerate from 0 to 60 mph in 7.1 seconds. An advanced variable-vane mechanism allows the engine to achieve higher power at lower cylinder pressure.
A new vehicle air intake system with hood scoop delivers cool air into the engine. This helps the engine run better, especially when towing or driving up steep grades. An exhaust brake slows down the vehicle, thereby reducing wear and tear on the vehicle’s regular braking system.
The engine does suffer from several faults including: overheating, premature injector failure, chafing of the injector harness, and a transmission limp mode that goes into effect randomly. The potential issues could also be engine oil incorrectly being in the turbocharger, air wrongfully being in the fuel lines, and fuel starvation.
Cummins Turbo diesel I6
The Cummins I6 is a straight-six, 24-valve turbo diesel that has been updated for improved responsiveness and handling. These improvements come while also providing low noise and vibration. This engine leads in torque ratings and towing capability. In 2019, Cummins achieved 1,000 lb-ft. of torque and can tow up to 35,100 pounds and haul up to 7,680 pounds.
The I6 is an inline engine and the other engines mentioned are V8s. Compared to V8s, inline engines are simpler, requiring just one cylinder head and one valvetrain. There is also more room inside the engine compartment, which makes them easier to repair and maintain.
It comes available in either 4×2 or 4×4 configurations and with an Aisin AS69RC six-speed automatic transmission.
Problems with the Cummins 6.7 often come down to emissions parts, such as a diesel particulate filter (DPF) that keeps clogging, the EGR (exhaust gas recirculation), or the fuel dilution. The turbo and head gaskets have also been reported to fail as well.
In 2011, in the same year Chevy and GM introduced the Duramax engine, Ford debuted a new Powerstroke engine. Ford developed this new engine without Navistar – their former engine partner.
This engine features DualBoost variable geometry turbo, a steel crankshaft, a water-to-air intercooler, the Instant Start feature, and a common-rail injection system. It even includes new piston jets that cool engine components and prolong their lives and a compacted and deep-skirt graphite iron engine block. This component is lighter in weight than predecessor models.
Other upgrades over previous models include the inclusion of an IROX coating on the lower main bearing, a heavier crankshaft damper, a fan clutch update, an EGR cooler flow, and turbo updates to support additional power and torque.
Issues with the Powerstroke include CP4 Bosch pump failures which contaminate the entire fuel system with metal shavings. This problem can cost you up to $9,000 to repair. Other issues occur when air enters the fuel system during fuel filter replacement, the truck goes into neutral for a second or two when shifting gears, the fan clutch won’t turn on at high temperatures, and the truck will start shaking during normal operation for no apparent cause. Truck owners call this known problem the “death wobble”.
Of course, much of this criteria favors larger engines, and each manufacturer mentioned here makes class-leading engines with smaller capacities than the ones mentioned in this article. However, if you are driving a larger pickup truck then you now know your top 3 options for engines that are long lasting, reliable, and will keep you out of the shop for costly repairs.