9 Semi Trucks With The Best MPG

When it comes to work trucks, it's fairly well known that even the most fuel-efficient pickups get fewer miles per gallon than their passenger vehicle counterparts. This logic extends even further when the size of the truck gets larger — despite putting almost exclusively highway miles on the engines, semi-trucks get fairly abysmal fuel economy. The reason is pretty straightforward. These trucks are much larger than even work-oriented pickup trucks, and they tow a whole lot more cargo. The combination of their larger size and larger loads results in lower fuel efficiency. 

Just how low are we talking about? The average is somewhere between 7 and 8 mpg. In 2018, NACFE reported that 7.28 was the average with a mixture of older and newer trucks on the road. This is something that semi-truck makers have been working on and anecdotal evidence suggests that truckers with newer wheels are doing a fair bit better than average. 

The newest semi-trucks get the best fuel efficiency, generally. However, if you want to know more than that, we have a list below. Fuel efficiency is difficult to find for semi-trucks because there are so many variables to take into account. For example, driving through the mountains will result in lower fuel economy most of the time than driving on the plains. So, we looked at as much data as we could and the list below is what popped out. 

The Volvo VNL series semi-trucks are kind of a bit deal. They're easily among the most powerful trucks in the world, with a GVWR ranging up to 225,000 pounds if properly equipped and loaded. At its strongest, the truck can do 500 hp and 1,950 lb-ft of torque. It also benefits from Volvo's I-Torque system, which includes Volvo's D13TC engine. Among other things, the I-Torque system allows modern VNL trucks to get better fuel economy than their predecessors while still having plenty of power for those larger loads. That sounds like an advertisement but it's really just technology pushing forward. 

In any case, equipped with all this new tech, Volvo VNL trucks are rated to get 8.5 mpg or higher, depending on conditions. Per drivers on Fuelly, the real-life average is 6.0 and 7.5 mpg, which is still pretty decent. After all, one good drive through the mountains and it's game over for fuel efficiency. Currently, there are six variants of the VNL from the 300 to the 860 models, which may hurt its numbers somewhat. We assume a properly equipped truck under good driving conditions can easily exceed its rated 8.5 mpg figure. 

With its New River Valley plant in Virginia, Volvo operates the largest semi-truck facility in the world right here in the United States. That means the VNL trucks you can buy and drive here are made here, and they're competitive in terms of fuel economy with Mack and Western Star. 

Many trucks perform about as well as the Mack Pinnacle when it comes to fuel economy. Its diesel engine makes up to 505 hp and up to 1,900 lb-ft of torque. Among other things, Mack boasts that this truck has a gross vehicle weight (GVW) of 62,000 pounds and a gross combination weight (GCW) rating of 80,000 pounds. In short, this thing can haul a lot of stuff. 

For fuel economy, we've seen it rated as high as 8.0 mpg. For that measurement, we assume it's under favorable conditions. Real world fuel economy tends to be lower. On Fuelly, the Mack Pinnacle averaged 6.3 mpg in 2015 between five vehicles and 105 fill-ups. Believe it or not, that's about typical for semi-trucks these days, which is why the Mack Pinnacle is a good representation of what slightly above average fuel economy looks like. So, in short, there isn't much analysis here. The Mack Pinnacle gets about 6.3 to 8.0 mpg. 

There is some subject to debate, however. Mack has been making the Pinnacle since 2006. Mack has made improvements over the years, especially to the truck's MP8 engine. Thus, it stands to reason that a newer Mack Pinnacle performs better than the older ones, and the older ones may be dragging down the overall average. 

The Kenworth T680 is right about on par with its larger W900L sibling. Both big rigs use the PACCAR MX-13 engine. However, the MX-13 is the largest engine offered on the T680. It also has the optional PACCAR MX-11 engine that offers about 50 less horsepower and a little under 200 fewer lb-ft of torque. Thus, like any semi with multiple engine options, it's tough to figure out which engine actually does better in this arena. 

Based on its size and engine, fuel economy of 9.0 mpg is not unheard of in the T680, at least in optimal conditions. In real world use, Fuelly users users report getting somewhere between 6.0 and 8.0 mpg, with a few reporting above and below those figures. So, much like its W900L cousin, the fuel economy numbers are a little all over the place but seem to average out at around 7.0 to 8.0 mpg. Of the two, we saw more consistency with the T680, so we listed it higher than the W900L. However, the W900L had the higher mpg reported between multiple drivers, so it got the win. We'll talk more about that shortly. 

Based on the data we could find, it seems the MX-13 is the more fuel-efficient engine while the MX-11 is the less expensive option. Either way, the truck is capable of above average fuel economy numbers, which bodes well for owners. 

The Kenworth W900L is one of the largest trucks on the list, stretching a little over 11 feet from the bumper to the back of the cab. This gives drivers tons of space to drive, sleep, and make those long hauls. The truck comes equipped with one of two engines. The first is a Cummins X15 that makes 600 hp and 2,050 lb-ft of torque and the other is a PACCAR MX-13 that does 510 hp and 1,850 lb-ft of torque. It also comes with a few transmission options, giving drivers the chance to find the truck they want. 

Regrettably, we were unable to find fuel economy numbers for each engine and transmission combination. On paper, the W900L should roughly the same fuel economy as the Kenworth T680 since they both share the PACCAR MX-13 engine option. That figure is roughly 7.9 mpg. However, real-world testing shows that it tends to underperform those numbers at around 6.4 to 6.8 mpg. On Fuelly, we saw that the 2023 model scored an excellent 9.7 mpg across three vehicles reported, but in most years, it was under 6.0 mpg. 

All told, the numbers are all over the place, with it ranging from 6.4 mpg to 9.7 mpg. On the low end, that's about average, but that 9.7 mpg high is actually pretty impressive for a truck that huge. 

The Western Star 57X was introduced in 2022 to replace the 5700XE, which was only six years old at the time of its retirement. Improvements over its predecessor included a more aerodynamic hood and an overall design that shaves off roughly 1,000 pounds of weight. The truck offers three engine options: the Detroit DD13, DD15, and DD16. With multiple engine options comes multiple fuel economy estimates and power figures. At the top end, the 57X can output 600 hp and 2,050 lb-ft of torque. 

With multiple engine options, it made the fuel economy a little difficult to pin down. With the standard DD15 engine, the truck managed 7.8 mpg in a test drive conducted by the Commercial Carrier Journal. However, the writer noted that this was also after being stuck in traffic for 45 minutes, and that they anticipate that the truck can do better. After some surfing, we found an example on Reddit of a user getting 9.5 mpg after a 1,700-mile haul, which backs up the reviewer's assessments. The truck is still too new for Fuelly data, so we're comfortable with saying that it's somewhere between 7.8 and 10 mpg. 

Overall, it's not a bad showing for a truck that doesn't have the name recognition of larger brands like International or Mack. It's above average for sure, especially if driven in optimal conditions. We expected no less from a truck that officially didn't hit the market until 2024.

The Peterbilt is right up there with some of the best on this list in terms of fuel efficiency. This particular truck uses a PACCAR MX-12 engine paired to a PACCAR TX-12 Pro transmission, producing up to 605 hp and 2,050 lb-ft of torque. Between that and the rest of the design, Peterbilt 579 models can carry some serious cargo. 

For fuel economy, the highest total we've seen is 10.7 mpg, although to be fair, that is Peterbilt's super truck that is basically a modified 579. In real world use, the truck gets somewhere around 6.0 to 6.5 mpg on average per Fuelly while other sources say that the truck does just under 10 mpg. So, not quite 10 mpg, but skilled drivers can probably eclipse the double-digit mark with careful driving on a flat road. 

The numbers are pretty good considering the truck was released in 2012, which is older than some other models on the list. Based on what we've seen on Fuelly, the numbers seem to hold up over the course of the 579's entire life with some of the best numbers coming from models built in the 2010s. Thus, for used semis, the Peterbilt 579 is arguably among the best when it comes to fuel efficiency, but as usual, where it's being driven matters too. 

The International LT625 is the most fuel-efficient semi that the brand currently sells. We say currently, because there is a super truck in the works that's expected to get much better fuel efficiency (more that later). Powering the LT625 is International's S13 integrated powertrain, which pulls along the semi with 515 hp and 1,850 lb-ft of torque, and includes the engine, transmission, and aftertreatment system all in one package.

Unlike most trucks, the International LT625's S13 powertrain has been tested numerous times. Drivers from Pilot Flying J posted about their tests with the powertrain, achieving a best of 8.59 mpg and a low of 6.79 mpg in less-than-optimal conditions, with a total average of 7.74 mpg. Maxim Truck and Trailer posted its tests, which lasted over a year and apparently involved over 43 fleets — the powertrain averaged 9.44 mpg with a high of 10.10 mpg. All this is to say, the LT625 and its S13 powertrain make an excellent combo. 

In fact, International is so proud of its S13 powertrain that it offers a $2,500 gift card to truckers who can't achieve good fuel economy with it. It's a good deal, especially from a company that's been around since the 1830s. It was also among the most consistent in that we were unable to find any record of the truck getting bad fuel economy, which is unusual given how uneven the ground is. It's a shame the company stopped making pickup trucks. 

The Freightliner Cascadia Evolution is where things really get serious. It's already well-known as one of the most fuel-efficient semi-trucks that money can buy. If this list didn't include a couple of prototype semis with exceptional fuel economy, the Cascadia would be at the top. In terms of trucks you can buy today, you can't go wrong with one of these if you want good fuel economy. 

This is the one of the only semis on the list to top 10 mpg. In all fairness, Southport Truck Group accomplished this feat on a test track in optimal conditions, but as you've no doubt seen so far, double digit fuel economy is a rarity in this space. That same test returned 9.31 mpg on a cross-country drive. Real world fuel economy tends to vary, with a lower 6.2 mpg average as reported on Fuelly, and a few anecdotal stories on Reddit of people getting around 8.3 mpg. Basically, there are Cascadias out there getting average fuel economy, but most are scoring quite a bit above it. 

What's doubly impressive is that the Cascadia does it with the same engine options as some other semi-trucks, running on the Detroit DD13 and DD15 paired to Detroit DT12 transmissions. That's the same powertrains as the Western Star 57X, and a few others. It just goes to show what improved aerodynamics can do to a semi's fuel economy. 

Finally, we have two prototype semi-trucks, which happen to have same name, oddly. This one is the Kenworth SuperTruck 2. This highly designed semi is made with aerodynamics in mind, which is why it bears a small resemblance to the Japanese bullet train. This beast uses a PACCAR MX-11 engine and a PACCAR TX-12 transmission like some other semis on the list, but it also comes with a mild hybrid system. Those, combined with improved aerodynamics, gives the truck its impressive fuel economy numbers. 

According to Kenworth, the semi can achieve a very impressive 12.8 mpg. It achieves this through the aforementioned hybrid system, aerodynamics, and a massive weight reduction of nearly 7,100 pounds. Kenworth developed the truck over a six-year period before showing it off at the ACT Expo in 2024. Thus, this truck is not in production, and you can't buy one. However, truckers' dream of a future with double-digit mpg all the time is getting closer.

With the way things are right now, Kenworth's SuperTruck 2 is the second most fuel-efficient semi that we're able to find. That's not bad for a truck that boasts only 440 hp and a 48-volt electric generator. Per Kenworth, the mild hybrid system doesn't even help turn the wheels. Instead, it runs the engine fans, HVAC pumps, and other things that are typically mechanically driven so that the engine can focus on spinning the wheels. 

International also has a SuperTruck II and it is the most fuel-efficient truck we can find. Like Kenworth's version, the SuperTruck II is still a prototype, but it gives us a glimpse into what might be someday. Its fuel efficiency is thanks to design refinement, various enhancements, and a hybrid system attached to International's S13 integrated powertrain system. That S13 engine was also refined for this truck, giving it even more efficiency. 

The result is a truck rated for an outstanding 16 mpg, which International says it achieved in real world driving conditions. Of course, that's likely under the most optimal conditions. Even so, we've seen the fuel economy of most other semis jump around by anywhere from 2-3 mpg. If this thing's topping out at 16 mpg, a real-world average of 10 mpg (or higher) doesn't feel unrealistic.

If International's claims about the truck's fuel efficiency are accurate, this would be a generational leap forward in fuel efficiency for semis, though it likely won't compete with electric powertrains when they get introduced eventually. International has already said that this is just a stepping-stone to total electrification. There doesn't appear to be release date but given that this and Kenworth's trucks are built on powertrains that already exist, it should come out eventually. At that point, truckers will have the option to virtually double their fuel economy depending on which truck they already drive.