5 Of The Best Cummins Engines Ever Made

Ever since the company was founded in 1919 by Clessie Cummins, Cummins engines have been powering automobiles, farm equipment, industrial machines, and more. The company did well for many years, but it really became a household name in the 1980s when it started putting its diesel engines in Dodge Ram trucks. This break into the mainstream market did little to deter Cummins' industrial operations, and it continues to make engines for semi-trucks, tractors, and more to this day. 

With so much history, it's difficult picking out the greatest Cummins engines of all time, especially because the company has continually improved its engine designs to this day. After all, this company keeps its fingers in a lot of pies — you can even find a 3,400 hp Cummins engine in the modded segment, placed in a truck that does a quarter mile in under 5 seconds.

To make things easier, we'll skip over the iconic Model F, Model U, and Model K engines of Cummins' early days and focus a little more on some of the stuff its done more recently. Yes, these are mostly work-oriented engines but there will also be a race engine in here too, and it was a pretty good one for its day.

Cummins most recent engine is arguably one of its best. The 6.7-liter ISBe Turbo Diesel is the current flagship product from the brand. Much like its predecessor, which we'll get to shortly, the 6.7-liter is still mostly shoved into Ram trucks to this very day. The 2025 models of the Ram 2500 and 3500 HD are the most recent models to use the engine. The Ram 1500 used to come with a 3.0-liter EcoDiesel V6, but it has since been discontinued. 

The Cummins ISBe is a really good engine. It outputs 420 hp and 1,075 lb-ft of torque, making it excellent for heavy duty pickup trucks, and Ram trucks equipped with it are among the best when it comes to towing. In addition to trucks, a special variant of the 6.7-liter is offered as a school bus engine. It also joins the X15, X12, and L9 as an option for motorhomes and RVs. Like the 4BT and 6BT, there is also a special variant for marine use. 

It's likely that the 6.7-liter is also used in agricultural and industrial settings, but those use cases are not as well documented. In any case, this engine is the one that you're most likely to run into if you're buying something new since it's the one that Cummins makes. The engine has been around for well over a decade, but has seen steady improvements to stay ahead of competitors and emissions regulations. 

Once upon a time, Cummins actually participated in racing events. In fact, it did so for many years. The brand had some of the first four-stroke engines in Indy racing history back in the 1930s, just a few years founder Clessie Cummins himself drove 14,600 miles at the Indianapolis Motor Speedway in a Model H-powered car. However, we'd argue that the best engine from the Indy racing era of Cummins was in 1952. That year, Cummins ran a car with the JBS-600 engine. It went on to become about as legendary as an engine could get back in those days. 

For starters, the JBS-600 achieved 139 mph at Indianapolis, which was a record at the time. It was also the first turbocharged engine (and only diesel) to run in the race, so it may have had a bit of an advantage over the rest of the cars. The JBS-600 featured 430 hp, which is a wild amount of horsepower for the 1950s when most consumer engines were putting up less than 200 hp. Despite its record-setting power and race-first turbocharger, the car was unable to finish the race due to damage that cause of which remains a mystery to this day. 

This car did see a brief return to glory when famous racer Mario Andretti gave it another drive at the 2022 Indy 500. The Cummins JBS-600 remains to this day the only diesel engine to ever capture a pole position at an Indy event. 

In addition to trucking and racing, Cummins has a decently big footprint in the agricultural space. The documentation for these engines isn't nearly as well kept as it for those powering commercial trucks or racing cars, so we don't have a huge list of engines used for agriculture. However, the company is known to have powered the first diesel-powered tractor with its 60-hp Model U engine. That particular tractor was a one-off, however, and never made it into production. It wasn't until the 1950s when Cummins started getting big in the tractor game with its engines reaching upwards of 12.2 liters and 150 hp by the end of the 1950s. 

Cummins still makes tractor engines today and its most recent offering include the L9 engine, which you'll see in farming tractors along with the QSK19 engine. The latter is a 19-liter six-cylinder behemoth that outputs up to 700 hp and 2,032 lb-ft of torque, making it even more powerful than the brand's X15 engine for semi-trucks. These engines, along with the L9, are tucked into tractors, combines, sprayers, and other, more specialized agricultural equipment. There are smaller variants available as well for more modest applications.

In addition to agriculture, Cummins engines are featured in other types of tractors, like the ones that pull airplanes onto the runway. Some of those tractors were modded and raced, with one example being the Wild Thing II, a tractor with a modified Cummins N14 engine that did 525 hp and over 1,000 lb-ft of torque. 

It would be bad manners to construct a greatest engines list for Cummins and not mention something from the commercial trucking industry. There are many engines to choose from here. The H672 was first built in 1932 and dominated the commercial trucking space for decades. By 1951, more than half of all commercial trucks ran a Cummins diesel. The brand was already making turbodiesels by then that were reaching 175 hp. Even today, many Cummins engines are used in commercial trucking, including the F3.8, which is popular in Brazil, Russia, and China to this day. 

For this list, we'll talk about the most recent engine in that prestigious lineage, the Cummins X15. This is the most modern and powerful commercial truck engine that the brand builds and is paired with the X12 engine to give truckers two good offerings. The X15 boasts up to 565 hp and a monstrous 2,050 lb-ft of torque, which shows just how far turbodiesels have come in the last 70 years when compared to the 175-hp diesel of the 1950s. In short, Cummins may have more competitors than it used to, but it still makes a great engine. 

The X15 powers some of the best semi-trucks on the market, including the Kenworth W900L, some models of the International LT625, and others. You've no doubt driven by a truck powered by a Cummins X15 or X12 if you've been on a long highway jaunt in recent memory as they remain a popular engine choice to this day. 

The Cummins 5.9-liter inline-six, also known as the Cummins 6BT, is one of the most important turbodiesel engines in history. Cummins started making the engine in the 1980s for various uses. It might have ended up as a footnote in the grander scheme of things if not for what would come at the end of the 1980s. Cummins struck a deal with Dodge to include the turbodiesel in its Ram series of trucks. This move is largely credited for revolutionizing the turbodiesel in the modern work truck, a trend that virtually every U.S. truck maker does to this day. 

Its inclusion in Dodge trucks was its biggest mark on history, but the 6BT was also used in just about everything else you can think of, including boats, trucks, and agricultural equipment. It's largely hailed as one of, if not the best turbodiesel engines ever made. Some of that glory is shared by other B-series engines, including the 6B (not turbocharged) and the 6BTA (turbocharged and aftercooled). However, the use cases were mostly interchangeable, so all the engines get credit. 

The 4BT, which is just a 6BT with two fewer cylinders, remains one of the most versatile engines of all time, being used in everything from marine to agriculture, construction, automobiles, industrial machines, and even power generators. It's difficult to understate the iconic value and versatility of the Cummins B-series engine. They were great at everything for decades and Cummins still sells them to this day, albeit for marine use mostly.