For countless fans of diesel, the brand “Cummins” has been the first name in diesel for decades. Since its founding over a century ago, diesel was the core of Cummins’ business. But now, Cummins has done something weird. Last week, the company announced its first gasoline engine. That’s weird enough, but Cummins says that its new B6.7 Octane engine is based on the legendary 6.7-liter diesel engine and all of this is actually pretty smart.
The modern diesel engine is a mechanical marvel. Today you can buy pickup trucks with glorious engines that pump out over 1,000 lb-ft of stump-pulling power. These same engines can also return fuel economy into the 20-mpg range even though the trucks they’re bolted to weigh as much as the Chrysler Building.
But the modern diesel has also lost its edge. Buying a diesel used to mean saving money at the pump and an engine so durable it could outlast humanity. However, diesel fuel is now more expensive than gasoline. Couple that with the higher costs of maintaining modern diesel emissions equipment, and diesel engines are making less sense with each passing year.
California and other states are also pumping the brakes on diesel with strict emissions regulations. Despite all this, diesel power still has a solid footing in several industries. The massive diesel engines that power locomotives, large generators, construction equipment, and highway semi-tractors remain the kings of their segments. Diesel also still has its place in heavy-duty pickup trucks.
But what if you could have it all? What if you could have an engine with easier maintenance and fewer emissions equipment needs that go with gasoline consumption, while delivering the durability and power of a diesel? That’s more or less what Cummins is pitching with its new B6.7 Octane gasoline engines. By starting out with a diesel engine platform and adapting it to gasoline, Cummins believes it has created the ultimate workhorse.
The B6.7 Octane has a lot going for it on paper. It runs on 87 octane pump gas and has the potential to breathe some new life into internal combustion in commercial vehicles. From my seat here, I also see the B6.7 Octane as a potential solution to the California regulations that may kneecap diesel motorhome sales this year. Many of these coaches could get Cummins gasoline power!
It’s amazing that Cummins, founded in 1919, has gone this long without making a single production gasoline engine. The history of Cummins is chock-full of great diesel feats and even some alternative fuels like propane and natural gas, but it might be shocking to read that Cummins is getting gasoline engines, something it’s not at all known for.
In 2022, Cummins launched what it called its “fuel-agnostic” engine strategy. According to trucking journal CCJ, the goal of the Cummins fuel-agnostic strategy is to create a bridge between the heavy diesel engines of today and the heavy electric motors of tomorrow. The company recognizes that electric power is not yet ready to take over from diesel, so until electric and battery tech reaches that point, Cummins wants to offer other ways of reducing emissions and operating costs in everything from school buses to highway tractors.
Cummins sees the fuel-agnostic strategy working for a variety of its engines ranging from Ram truck engines to the big boys you’ll see churning away in straight trucks and RVs. In 2022, it was expected that Cummins’ first engine based on this new architecture was to be based on the B6.7 diesel found in Ram pickups and medium-duty trucks. However, Cummins also wanted to apply the new tech to the L Series and X Series engines used in bigger rigs. The goal is that when a customer orders a truck with a Cummins engine, they’d get their choice of diesel, natural gas, hydrogen, propane, or gasoline. To be clear, these aren’t multi-fuel engines. Once you order your engine it runs only on whatever fuel you chose for it.
In 2024, Cummins renamed this project to “Higher Efficiency, Lower emissions and Multiple fuels,” or HELM, and it has the same goals as the fuel-agnostic engine project.
How it works is pretty neat. To create the new architecture, Cummins started with existing platforms. Cummins says that the components below the heads of the base engines are supposed to be similar across the lineup. In other words, the bits under the head of the B6.7 Octane should be bits largely similar to what you get in the B6.7 diesel straight-six that powers hundreds of thousands of trucks.
The parts commonality is pitched as not only a way for Cummins to make a variety of engines easier, but for fleet operators to have an easier time. In theory, a B6.7 Octane may have a similar diagnosis tree as a B6.7 diesel, at least under the head, anyway. Cummins also sees the B6.7 Octane as having diesel-like service intervals and saving fleets additional money as they won’t have to re-tool service departments just for the gasser.
Cummins is tight-lipped about the exact changes necessary to make the B6.7 platform to run gas, but thus far says that most of the changes are in the head. For now, Cummins really wants you to know how big of a deal the engine is:
The Cummins B6.7 Octane – Cummins’ first gasoline-powered engine is purpose-built to deliver the highest durability of any medium-duty gasoline engine on the market.
The Cummins B6.7 Octane engine is specifically designed and developed for the medium-duty market while achieving 2027 EPA and CARB compliance. Expanding the legacy of the Cummins B-series platform, the B6.7 Octane is equipped with the power, durability and performance of diesel with the simplicity of gasoline.
Cummins has also provided a handy sheet for both the gas and propane variants of the B6.7:
The company goes further and says this is the only purpose-built gasoline engine in the medium-duty truck market, and that it gets up to 10 percent better fuel economy than other gas engines in medium-duty trucks. The biggest advantage, Cummins says, will be in maintenance. The B6.7 Octane has passive catalysts for emissions controls, and that means no DPFs and no DEF to worry about anymore. According to Cummins, the engine should only require the kind of maintenance expected for a gas engine in a pickup truck.
This engine is also supposed to work a bit like a diesel. Cummins is currently quoting a maximum horsepower rating of 300 HP with max torque pegged at 660 lb-ft. Now, the truck engine nuts among you might find these numbers interesting. The horsepower rating is far lower than the 430 HP on tap in the Ford 7.3-liter Godzilla V8, but the twist in the Cummins is better than the Godzilla’s 475 lb-ft. Again, that’s by design. Like a common diesel engine, the Cummins straight-six gasser is supposed to make substantially more torque than horsepower.
Cummins also says it has been testing other power outputs, including 200 HP and 600 lb-ft of torque and 220 HP as well as 260 HP. Both of those latter power figures would also pump out 600 lb-ft of torque. However, the company says that aside from the max power figures, exact ratings have not been determined just yet.
Cummins says it’s also targeting the same transmissions found in medium-duty Cummins 6.7 diesel pairings, notably the Allison 2000 and 3000.
The company hopes to drop these engines into pickup trucks, school buses, step vans, delivery vehicles, and service trucks. For now, the launch customer is Kenworth and the truck maker says it’ll be putting these engines into Class 5 through 7 conventional trucks beginning sometime later this year. One early review seems to suggest that these engines do perform like diesels, too, which is awesome. Take a listen to that soundtrack! It’s like a diesel, but not:
That being said, I probably wouldn’t expect a 6.7 straight-six gasser to be around for a very long time. Cummins acknowledges that internal combustion engines might be living on borrowed time:
Cummins HELM platforms are a key component of a broader Destination Zero strategy. This ambitious plan focuses on achieving zero emissions by investing in cutting-edge technologies and improving internal combustion engines (ICE) to reduce emissions in the near term while preparing for a zero-emissions vehicle future.
Destination Zero is built on the understanding that decarbonization is a journey, and different industries and regions will move at different speeds. Cummins has adopted a balanced approach, continuing to enhance ICE technology for immediate gains in efficiency while also investing heavily in hydrogen fuel cells, battery electric systems, and other future technologies that will drive the transition to zero-emission vehicles.
As silly as all of this might sound, it’s actually not that crazy. Some might want to draw parallels to the 1970s when General Motors used gas engine architecture to create diesels. But that’s not the only time when an existing architecture running on a different fuel source was converted to something else. Notably, Kawasaki has been building prototype hydrogen engines out of the architecture of the gasoline H2 motorcycle engine.
This isn’t even the first time a Cummins has been made into a gas engine. Back in the 1960s, the White Motor Company was convinced that gasoline engines were the future, not diesel. In response, the company took 500 cubic inch Cummins diesel engines and converted them to gasoline. The “Giesel” and the White Trucks Mustang VIII, as they were called, allegedly used lower compression pistons and placed spark plugs where the diesel injectors used to live.
Cummins is technically correct when it calls the B6.7 its first gasoline engine since White converted the Cummins engines into gasoline, not Cummins.
As of right now, Cummins hasn’t made any mention about the future of where this engine could end up. The company figured it could put a 6.7 gasser into a pickup truck, but no official announcement about that exists at this time. But if this goes well, who knows where we could see these engines.
Images: Manufacturers
Top graphic images: Cummins; Wavian USA
Maybe they can put them into the Chevy Express vans and keep the good feelings rolling for a few more decades.
The most successful diesel to gasoline conversion was Landrover’s 4 cylinder engine which started as a diesel in 1957, became a gas engine in mid 58 and stayed nearly unchanged until 1985
I’m not familiar with diesels, but I’ve never seen “controllable piston cooling nozzles” advertised before. I could see that being helpful for preventing burning up cylinders with the ultra-high compression diesel cycle, but curious how it applies to gasoline applications.
Any explanations on that?
Probably in the opposite way,i.e that it shuts down the piston cooling gallery in low-load situations to aid in efficiency and to control temperature. That is probably a better solution than blocking it off entirely too,since it’s already there in the first place.
Piston cooling nozzles have been common on turbocharged gas engines since at least the 80s, working just the same as they would in a diesel to control piston temp. Cummins has added control to the system to allow the engine management more control over piston temp based on demand.
I love this outlook. This is the kind of balanced view on electrification that I wish more people had. Will electric vehicles ever solve all needs? Not likely. Can we make internal combustion as good as it possibly can be while electrification technology continues to advance? Absolutely.
Can they be used in harmony with each other to make a greater sum of their individual parts? Also yes.
I was hoping for the Ram HD update they’d just shoehorn the gasser 6.7 in there, especially with the diesel getting the 8-speed, it could make for a super simple production line.
I can always dream though!
Like the idea, but doubt the hp numbers will appeal to buyers in that application. Maybe they can get more than 300 out of it down the line
If people are buying HD trucks for the horsepower, they aren’t buying the right product.
Less horsepower means lower towing ability unless you don’t mind doing it at lower speeds and higher rpm.
Besides the fact that I highly doubt you couldn’t tow at 70mph with “only” 300hp when you would have about 660ft-lbs of torque and 8 gears, 300hp is only 130 less than the best 6.7 diesel will produce, and last I remember, the diesels always get rated for the most weight to tow. So, while it may not be able to haul 30,000 pounds, it’s not going to make a 2500 or 3500 only tow 7,000 pounds like a 3.6. It’d still likely out-tow a Hemi.
These HP numbers are similar to that of diesel engines in the early 2000’s. (6.0 Powerstroke, original Duramax, etc.) While torque is about 100 lb/ft more than that time frame. This engine, if it still provides a nice flat torque curve similar to a diesel, will still perform very well at towing. BUT, I also agree many pickup buyers will turn up their nose at the lower power numbers. Not because of it capabilities or perceived lack thereof, but simply because “BIG N0MBR MOR GOODER HOSS. SMOL NOMBR BAD!!!11!”
Yes please. I have to drive just shy of 10 miles to get diesel for my wife’s truck, it’s part of why I bought an old ford with a 460. I used to have a pre-def cummins and loved it.