Have you ever thought about getting a Truck with a diesel engine? I admit that I never thought about it much myself. But the more I learned about diesel and its advantages over gasoline engines, the more diesel engines piqued my interest.
Diesel engines are known for their toughness. They’re big engines for big vehicles. But if you make the investment, you’ll quickly come to appreciate their superior durability and fuel efficiency. So, if you want to be a working-class hero, try out a Super Duty Ford truck with a rugged and reliable diesel engine.
We’ll cut to the chase and tell you that the 6.7L Turbo-Diesel Power Stroke engine, released in 2019, is the latest and greatest Ford Diesel engine ever made. We’ll go over all the different models of the Power Stroke and see precisely why the 6.7L Turbo was such a great leap forward compared to its predecessors.
Diesel vs. Gasoline
In case you’re not familiar, let’s do a quick rundown of the differences between diesel and gasoline engines.
A diagram showing how Gasoline, Diesel, and HCCI engines are ignited. Source: Capital Reman Exchange.
Both are internal combustion engines that convert chemical energy—stored in the chemical bonds of the fuel—into mechanical energy. Mechanical energy moves the pistons inside the engine cylinders. This, in turn, moves the wheels of the automobile. Chemical energy is converted via a series of small explosions inside the engine (hence the “internal combustion” part).
Gasoline engines mix fuel with air, compressed by the pistons, and finally ignited using the spark plugs. Diesel engines compress the air first, which causes it to heat up. (That’s Boyle’s law, remember? From high school chemistry? Pressure is directly proportional to temperature.) Fuel injected into the compressed air ignites immediately with no spark plug required.
Diesel and gasoline are both fractional distillates of petroleum oil. While the technical differences between the two are a bit hard to explain, the gist is that diesel is refined to be injected into compressed air, while gasoline is made to resist igniting until a spark is presented.
Diesel contains more chemical energy than gasoline and provides better fuel economy overall. It is, in fact, one of the most efficient fuels available today. This efficiency also comes from how diesel engines function. While a gasoline engine simply expels the heat as waste energy through its tailpipe, a diesel engine can convert heat into mechanical energy and use it to power the vehicle. It provides far more torque than its gasoline counterpart.
Typically, an engine will get 20% to 30% more mileage than a comparable gasoline engine. Diesel engines can even outpace the fuel economy of hybrid gasoline-electric vehicles, under the right circumstances.
However, gasoline engines are capable of much higher top speeds. This is because, while diesel engines must wait for air to heat up and ignite under pressure, the spark plug in a gasoline engine can quickly ignite fuel and convert chemical into mechanical energy with less compression required. Because gasoline engines need less compressing power, they are typically much lighter, further contributing to their higher top speeds. This is why gasoline engines are preferred in non-commercial automobiles such as cars and motorcycles.
Nowadays, gasoline is cheaper than diesel. This is largely because of high demand for diesel fuel among commercial shipping companies, home and industrial generators, and as heating oil.
Power Stroke Engines
Power Stroke is a family of engines made by Ford since 1994. It is easily one of Ford’s most prominent and popular types of diesel engines. Ford Autoworks in Ithaca, NY described the Power Stroke as the “yardstick” standard truckers use to measure the power and performance of engines.
There have been several versions throughout the years, from the original 7.3L to the 6.0L, the compound turbo 6.4L, and more recently the 6.7L Turbo-Diesel Power Stroke. We’ll also look at 3.2L and 3.0L engines at the end of this article.
7.3L Power Stroke
The first Power Strokes were collaborations between Ford and Navistar, which then went under the name of International Truck and Engine Corporation (ITEC).
The first such engine to hit the market was the 7.3L. It is known to this day as one of the sturdiest and most reliable diesel engines ever produced.
The 7.3L Power Stroke. Source: Dust Runners Automotive Journal.
Its specifications are as follows:
- Power: 275 HP
- Torque: 505–525 lb-ft
- Bore: 4.11”
- Stroke: 4.18”
- Block: iron
- Head: iron
- Compression Ratio: 17.5:1
Originally introduced in 1994 as the Ford rebrand of the Navistar T444E turbo diesel V8, the 7.3L remains the preferred choice for pulling heavy loads. It was more powerful and fuel efficient than any other diesel engine at the time of its debut.
However, new emissions standards forced Ford to pull the plug on production in 2003. It was replaced by the 6.0L and then the 6.4L, which finally inspired Ford to end their partnership with Navistar.
6.0L Power Stroke
This was the second diesel engine used in Ford’s trucks and E-Series vans. While the 6.0L and 7.3L were offered simultaneously in 2003, eventually the 7.3L was discontinued.
Compared to the 7.3L, the 6.0L did a better job at meeting emissions standards. It was used Ford F-Series (2003–2007), Excursion (2003–2005), and E-Series Vans (2004–2010). Its specifications are below.
- Power: 325 HP at 2,800 RPM
- Torque: 570 lb-ft at 1,600 RPM
- Bore: 3.74”
- Stroke: 4.13”
- Block: cast iron
- Head: cast iron
- Compression Ratio: 18.0:1
6.4L Power Stroke
The infamous 6.4L Power Stroke. Source: Engine Builder Magazine.
This engine was introduced in 2008, in response to stricter emissions standards and certain questions regarding the reliability of the 6.0L.
- Power: 350 HP at 3,000 RPM
- Torque: 650 lb-ft at 2,000 RPM
- Bore: 3.87”
- Stroke: 4.134”
- Block: cast iron
- Head: cast iron
- Compression Ratio: 17.5:1
Though it was quieter and cleaner than its predecessor, the added emissions equipment proved to substantially reduce fuel economy and caused numerous other mechanical problems.
Ford and Navistar’s long and rocky relationship came to an end after the 6L and 6.4L Power Stroke engines met with overwhelming negative customer receptions. The 6.4L Power Stroke, in fact, is notorious among Ford enthusiasts as one of the worst diesel engines ever conceived. It was hard to maintain, and repair and certain problems (especially with cracking in its pistons) could completely destroy the engine if not fixed immediately.
Midway Ford Company in Roseville MN made this perfectly clear. “Don’t look at buying anything other than 6.7L,” they told us. “The 6L and the 6.4L are way too troublesome, don’t even consider buying one unless you’re a mechanic.” Both engines experience lots of problems and, for that reason, are extremely expensive to maintain. “Unless you got a lot of money, the 6.7L is the only way to go.”
After the venomous critical and popular reactions to the the 6.4L, Ford abandoned Navistar and began developing their own Power Stroke engines. Here we’ll look at some of the best Power Stroke engines developed in the post-Navistar days.
6.7L Power Stroke
Despite superficial similarities, the 6.7L is a very different engine from the 6L and 6.4L. Introduced in 2011 and built in-house by Ford, the 6.7L incorporates a Bosch common-rail injection system and is made of cast aluminum and compacted graphite iron. The graphite iron offers excellent weight savings, making this engine sleeker and even more powerful. It has a larger bore and stroke than the 6.4L but with a slightly smaller compression ratio and lighter heads. It has 4 pushrods per cylinder, whereas the 6.4L had only 2. In sum, the 6.7L is easily the most powerful Power Stroke yet made.
The 6.7L uses a high-pressure common rail with Bosch CP4.2 injection pump (8-hole nozzles) as its fuel injector. The CP4.2 is notable for its ability to produce over 30,000 PSI of injection pressure. The 6.7L also features a cooled exhaust gas recirculation, diesel oxidation catalytic converter, diesel particular filter, and selected catalytic reduction for its emissions system.
The 6.7L has had two different turbo chargers throughout its life. First came the Garrett GT32 SST, which was a waste-gated variable geometry charger. This turbo charger lacked low-end power and occasionally was prone to overspeeding failures. Since 2015, the 6.7L has used a Garrett GT37 turbo charger. This charger is more reliable and can support more power than the GT32 SST. While neither can quite match the power output of the 6.4L’s turbo charger, most Ford drivers would agree that their increased reliability is well worth the trade.
The newest version of this engine, the 6.7L Turbo-Diesel Power Stroke, features a V-8 layout and the following specs:
- Power: 450 HP at 2,800 RPM
- Torque: 925 lb-ft at 1,600 RPM
- Bore: 3.9”
- Stroke: 4.25”
- Block: compacted graphite iron (CGI)
- Head: cast aluminum with reverse flow
- Compression Ratio: 16.2:1
This latest version of the 6.7L delivers vastly improved torque and HP alongside top-class fuel economy, and improved towing and payload capabilities. What’s especially impressive is that Ford achieved these enhanced specs purely by fine-tuning the engine control software, without making any physical changes to the engine since the previous 6.7L design.
In sum, the 6.7L is an upgrade to the previous 6L and 6.4L in nearly every way. Every Ford dealer we talked to said the same thing: get the 6.7L, don’t even think about getting an older model. It’s lighter, stronger, miles more dependable, and more efficient.
Sources: Dust Runners Automotive Journal; phone interview conducted with Midway Ford Company (06/22/2020).
Bonus Feature: The 3.2L and 3.0L Power Stroke Engines
A Power Stroke 3.2L engine, lovingly referred to as “The Puma.” Source: Ford Authority.
Two more Power Stroke engines have been made since the 6.7L, both in-house by Ford without input from Navistar.
The 3.2L Power Stroke is an inline-five engine that first hit the market in 2015. It is not a direct successor to the 6.7L but rather is more of a lateral shift in functionality, focusing more on medium-sized cargo vans. It is used in the Ford Transit, for example.
Ciocca Ford in Quakertown, PA told us about this engine’s specific uses. “The 3.2L came out for utility vehicles, and it’s mainly an SUV type motor,” they said.
Based on the Ford Duratorq engine (introduced in 2000), the 3.2L was adapted to meet American emissions standards and sold under the Power Stroke name.
- Power: 197 HP at 3,000 RPM
- Torque: 350 lb-ft at 2,500 RPM
- Bore: 3.54”
- Stroke: 3.96”
- Block: cast iron
- Head: aluminum
- Compression Ratio: 15.8:1
It is fitted with high-pressure common-rail fuel injection system and piezo injectors. It features variable geometry turbo, variable-flow oil pump, and cast aluminum low-friction pistons. This engine is notable for its excellent fuel economy and improved cooling during heavy-load situations.
The 3.0L Power Stroke, sometimes known as “the lion.” Source: The Fast Lane Truck.
The 3.0L Power Stroke Turbo-diesel V6 was introduced for the Ford F-150 in 2018. Though this engine had been available for the Land Rover Discovery and Land Rover Range Rover since 2014, this was the first time that the F-150—Ford’s best-selling pickup—was outfitted with a diesel engine. The specs of the 3.0L are below:
- Power: 250 HP at 3,250 RPM
- Torque: 440 lb-ft at 1,750 RPM
- Bore: 3.307”
- Stroke: 3.543”
- Block: compacted graphite iron
- Head: aluminum alloy
- Compression Ratio: 16.0:1
This engine is relatively small but still boasts an impressive power output and torque. The 3.0L was conceived as a medium-duty counterpart to the Ram 1500 EcoDiesel V6 engine and is known for its balance of fuel efficiency, power output, and performance. It can achieve up to 30 MPG on the highway.