Ranking the Best Diesel Engines Ever

As you guys might’ve noticed, we’ve made a lot of different articles about diesel engines. At the end of the day, there are a lot of really cool engines out there, but some of them are better than others, and because of that, I wanted to make a list of what I consider to be the best diesel engines of all time.

Keep in mind, this list isn’t in really any particular order because, quite frankly, I don’t think it’s fair to outright claim one diesel as the best of all of them because they all have pros and cons, and some are better at specific tasks than others.

#1 International DT466

Starting out this list is an engine we actually just made an article about recently, which is the International DT466, and again, this list isn’t in any particular order, so don’t consider this to be the best or worst engine on the list.

And really, what makes the DT466 worthy of being on this list are two things: its insane reliability and the fact that it completely changed the medium-duty truck market. Throughout its near half-century run and four different generations, it went through a fair amount of changes, but many aspects also stayed the same.

The best features which built the foundation of the DT466 and never changed include the super beefy, super heavy cast iron deep-skirt block, wet sleeve cylinder liners, incredibly strong connecting rods and rotating assembly, and big power capability.

The crankcase itself weighs a ridiculous 400lbs with massive bulkhead sections and main bearing surfaces. Simply put, International built the DT466 to be big, strong, and really hard to break. It’s heavier than all of its competition of the time while also not really making that much power, which is a recipe for a bulletproof engine.

Unfortunately, towards the end of its life, International was forced to add a lot of electronics and emissions systems to keep up with the EPA’s demands for cleaner engines, and ultimately those components did sacrifice some of its reliability. The base engine was still there and still reliable, but the electronics draped on top of it weren’t.

Where I think the DT466 really shines is in tractor racing, where there are plenty of examples of them making north of 3000hp with over 300lbs of boost pressure.

#2 John Deere 50 Series 6-619

And continuing with engines that dominate the tractor racing scene and are capable of making stupid amounts of power, we have the John Deere 50 series, and more specifically, the 6-619, which is the 619ci version of the 50 series engine. In the tractor world, a lot of people just call this the 619.

I know for a lot of you watching this, you probably haven’t even heard of this engine, and I will say this is probably the most obscure engine on the list, and honestly, in dead stock form, it’s really not that interesting. It’s pretty much just another big tractor engine that can put in decades of work reliably.

What makes this engine so interesting is the racing scene, where the top guys build these things with a billet block and 680 cubic inches of displacement, with some examples producing upwards of 4200hp at 4 to 5000RPM depending on the race and anywhere from 300 to 400psi of boost pressure.

In fact, this specific engine is one of the few engines you’ll find at any tractor pulling event that will regularly outrun the aforementioned International DT466. As I said, it might be obscure compared to some of the other engines on the list, but this engine has had a massive impact on the world of tractor racing.

#3 Cummins 6BT

Of course, no list of diesel engines would be complete without the 6BT Cummins or the 5.9L Cummins. When the 6BT Cummins first debuted in 1989, it was a game-changer. Even though it was stuffed into an outdated Dodge chassis, it gave the Ram trucks a new foothold in the pick-up truck market.

Offering 160hp, the 5.9L Cummins is pretty weak by today’s standards, however, at the time of its release, GM’s 6.2L diesel produced a mere 130hp and Ford’s Navistar 7.3L output 185hp. This put the Cummins right in the middle of its two competitors as far as horsepower, however, the Cummins output 400 lb-ft of torque, while GM’s diesel output 240lb-ft and Ford’s output 338lb-ft.

The 6BT’s foundation begins with a sleeveless cast-iron block with an integrated oil cooler, an oil pump cavity, as well as a camshaft bore that doesn’t call for pressed-in bearings. For increased wear resistance, the forged-steel crankshaft’s fillets and journals were treated to induction hardening, and the crank was anchored in place via 14mm main cap bolts.

Underneath the cast-iron head, you’ll find cast-aluminum, direction-injection pistons, which feature a large piston bowl for fuel to be injected directly into. Underneath the beefy pistons, you’ll find forged-steel I-beam connecting rods, which are necessary for coping with the massive torque at low RPMs. These stock connecting rods are capable of supporting up to 2,000lb-ft of torque.

Depending on the year you’re looking at, the turbocharger and injection system change a little bit, with the most prized versions equipped with the Bosch 7100, which is also known as the P-Pump.

I think its also worth mentioning that the 5.9 ISB engine, which is the 24 valve version of the 5.9L, is also an awesome engine in its own right, but if I had to pick one to be on the list, it has to be the 12 valve, plain and simple.

#4 7.3L Powerstroke

As you might’ve noticed, so far, everything on this list has been an inline-six engine, and as we discussed in-depth in another article, there’s a good reason for that, and there’s a reason most good diesel engines are inline-six, but with that said, there’s a few really good V8 diesel engine as well, with one of them being the 7.3L Powerstroke.

After Ford and International had seen success working together to supply the engines for Ford’s heavy-duty trucks with the 6.9 IDI, 7.3IDI, and then the 7.3IDI Turbo, we ended up with the 7.3L Powerstroke.

When Ford moved from the IDI Turbo engines to the Powerstroke engines, they ditched the mechanically driven injection system in favor of electronic injection. This was done for a number of reasons, but ultimately it helped them increase the power output while also decreasing emissions output.

Of course, switching the electronic injection upset some enthusiasts who love the simplicity of mechanically driven injection systems, but who cares it had to happen.

During its run from 1994.5 to 2003, the 7.3 Powerstroke was a huge success. Ford was selling more of their diesel-powered trucks than ever before, and they delivered everything their customers wanted with decent power and superb reliability. By the end of its life in 2003, this engine produced a respectable 275hp and 525lb-ft of torque which was miles ahead of the weak IDI Turbo engine before it.

But with GM dropping the LB7 on the world and Cummins dropping the 5.9L Common rail, Ford was behind the ball on power output compared to their competition. That fact, coupled with the impending emissions crackdown from the EPA, spelled out the death of the 7.3L Powerstroke.

While it’s far from the most advanced or powerful diesel engine we’ve seen in light-duty trucks, it’s arguably Ford’s most reliable and loved engine to be used in their F-series trucks.

#5 6.6L Duramax

That takes us to the third and final light duty truck engine on this list, and that’s the 6.6L Duramax. We could go even more specific and name something like either the LBZ or L5P Duramax as the best, but the thing, even though there are different generations of the 6.6L Dmax, they’re pretty much all the same engine with minor changes.

There’s been effectively zero major changes throughout the history of the 6.6L Dmax. There’s been no big changes to block, architect, head design, and more. There have been lots of small changes which we highlighted in our Duramax guide article, but for the fact that it really hasn’t changed drastically, I’d rather highlight the 6.6 as a whole on the list rather than one specific iteration of it.

I know some of you might be wondering why not the 6.2L or 6.5L Detroit Diesel engines that GM used prior to the Duramax, and I simply didn’t choose either of those because they lacked any form of major innovation, they barely made any power, and they didn’t really do much anything special at all.

With that in mind, this is the only engine on the entire list that uses aluminum cylinder heads, and it’s only one of two V8s on the list. When it first dropped on the market in the form of the LB7, it had more power and more torque than any diesel pickup up until that point.

A big part of why it was able to produce so much more powerful than anything on the list is simply because of its common rail injection system, which was the quietest and cleanest injection we had seen on a pickup diesel engine at that time. Of course, today, common rail injection can be found on pretty much all diesel engines, but back then, it was pretty wild to see.

#6 3406 CAT

Another engine that I think should absolutely be mentioned is the Caterpillar 3406, as it has become one of the most influential over-the-road truck engines of the few decades. Throughout the years, we saw a few different versions of this engine, with the 3406A, 3406B, 3406C, and finally the 3406E.

Depending on who you ask, they might claim one is definitely better than the other, and in my opinion, the E is the best of them all, as it combined the best of a simple and reliable base with also very reliable electronics and the addition of electronic injection also opened up the massive world of electronic tuning, which helped the 3406 grow in popularity even more.

The 3406 featured a bore of 5.40-inches, a stroke of 6.50-inches, and a displacement of 893 cubic inches (14.6L). Depending on the specific model you’re looking at, horsepower ratings ranged from 375-hp to 465-hp, with the highest rating coming in around 1,850 lb-ft.

Before the aforementioned E engine, we had the A and B engines, which were both mechanically injected, which for some people is their preference, as there are typically fewer parts to break on a mechanically injected engine, but for CAT to keep up with their competition and more specifically the EPA’s requirement for cleaner engines, they had to introduce the C engine, which was sort of a combination between mechanical and electronic injection.

Once they got the electronic injection system figured out and reliable enough for their liking, we got the E engine in 1993. Unlike the DT466 from International, which was ultimately ruined when they introduced electronics, Caterpillar managed to make the electronics on the 3406E incredibly reliable.

While the 3406 is no longer in production, it’s still being used all over the world, with many people simply rebuilding theirs when needed rather than upgrading to a newer engine with more emissions components.

#7 Cummins 855 Big Cam

That takes us to the next engine on the list, which is another super reliable over-the-road truck engine that basically completed dominated the market in the 1970s and 1980s, and that’s the Cummins 855 big cam.

The first big cam engines were introduced in 1976, and they were designed to replace the small cam 855 engines that needed to be phased out thanks to US government regulations regarding noise pollution and the Clean Air Act of 1976.

Although it was kind of forced to market due to Government restrictions, it actually ended up being super fuel-efficient, reliable, durable, and more powerful than nearly all the competition, which is what led it to become so popular.

The 855 ci Big Cam I used a 5.50-inch bore, a 5.98-inch stroke, and most versions were available with power ratings that ranged from 250 to 400 hp. However, some 855 Big Cam engines were rated as high as 605 hp in gen-set form.

The first three versions of the 855 Big Cam used Cummins’ pressure-time fuel system, which was unique from many other injection systems in the fact that it allowed for mechanically variable timing, which simply meant more power, better fuel efficiency, and reduced emissions output.

The Big Cam IV was introduced in 1985, but honestly, it wasn’t that good, and most people prefer the first three versions of the Big Cam, which is fine because the fourth version was quickly replaced with the Cummins N14.

Throughout the years, we saw upgrades, including a demand-flow cooling system and pulse exhaust manifold that debuted on the Big Cam II engine in 1979, a pressed-steel oil pan and Holset HT3B turbocharger added for the Big Cam III in 1983, and a revised cylinder head and pulse exhaust manifold for the Big Cam IV in 1985.

#8 Detroit Diesel 60 Series

But, before we saw electronic injection really take over the market, we had the Detroit Series 60, which was the first-ever heavy-duty truck engine with an electronic injection system when it came to market in 1987.

Think about it, most American cars were still carbureted at this time or using weird sorts of electronic throttle body injection, so to see this from a heavy-duty diesel truck engine at that time was literally unheard of.

With the 60 series, Detroit developed two sizes, an 11.1L and a 12.7L, and both of them were instant successes. Really, before these engines dropped, Detroit was losing market share and probably would’ve been out of business at the rate they were going, so you can credit the 60 series with not only saving Detroit Diesel but also being their most successful engine ever.

By 1992, a short five years after its launch, it was already the single most popular heavy-duty truck engine in North America, with applications ranging from trucks, boats, generators, emergency vehicles, and more.

Supposedly, Detroit Diesel worked with John Deere in the mid-1980s to fix their dying engine programs, but it’s unclear how much John Deere actually helped with the development of the Series 60. But, compared to the 50 series, it pretty much solved every issue and then some. By the time the 2000s rolled around, we saw a new 14L version of this engine which lasted all the way until 2011, when the Series 60 was phased out and replaced by the DD15.


So that’s some of the best diesel engines of all time, and I think it’s worth running over some of the honorable mentions, including the 6.7 Cummins, KTA Cummins, Mack E7, 1.9 TDI VW, Detroit Diesel series 71, and much more. As I said, the list is in no particular order, and there are many more engines I could’ve added, but for the sake of simplicity, I capped the list at eight engines.

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