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The inline-six engine may be a relatively niche engine configuration compared to more common inline fours and V6s, but it has plenty of advantages. One of the biggest is its balance, requiring no balancing shafts and making it inherently less susceptible to problems caused by odd vibrations, making it more reliable in the long run. They also have a tendency to make sizable power figures and have become a staple in luxury cars with performance leanings, like the BMW M3.

While the inline-six appeared to dwindle for a number of years, we’re seeing a resurgence of late, with arguably more straight-six engines available now than we’ve had in the last 20 years. With more variety to choose from than ever before, what do you use to separate these six-cylinder masterpieces? Is it fuel economy? Probably not, since no one chooses a six-cylinder for gas mileage when a four-cylinder will do. Power is the easy way to differentiate them, so we’ve ranked all the available inline-six engines on sale today from least to most powerful.

8 General Motors LM2 Duramax

Maximum Power: 305 hp

At the bottom of the list is the LM2 Duramax, a 3.0-liter diesel unit used in several GM SUVs and trucks including the Chevrolet Silverado and Cadillac Escalade. The former offered the LM2 engine for the first time in 2024, in the ZR2 trim level. Even though diesel engines have gained a less-than-stellar reputation in today’s emissions-conscious market, and their chief advantage of low-end torque is in danger of being provided more efficiently and cleanly by electric motors, there is still a place for them in the car world.

The LM2 Duramax was developed as part of a collaboration between GM and Opel, with most research and development work taking place in Italy; Opel also built three- and four-cylinder versions of the same engine family.

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7 Mazda Skyactiv-G 3.3

Maximum Power: 340 hp

The Skyactiv family of engines is well known for its focus on efficiency and sustainability; the Skyactiv-G 3.3 is both the first inline-six Skyactiv engine and the first inline-six produced by Mazda in general. It is available in two different power outputs and found in two similar-but-different applications. First introduced in the CX-90 SUV in 2023, it also powers the CX-70 here in the USA, and will be used for two similar SUVs in Europe called the CX-60 and CX-80. Mazda was originally believed to be plotting a rear-wheel drive sedan with this engine, but as the market shifted and SUVs grew in popularity, the sedan was axed in favor of SUVs with the new straight six.

The Skyactiv-G 3.3 also boasts the title of being the most powerful production engine ever built by the brand, although thanks to the Gentlemen’s Agreement of the JDM world, it is uncertain whether an earlier model might have unofficially beaten that record.

6 BMW B58

Maximum Power: 382 hp

A replacement for the N55, the B58 first arrived on the scene in 2015 in the first BMW 340i and is still in production today. BMW is the automaker most commonly associated with the inline-six engine, thanks to its century-long tradition of vehicles powered by an inline-six, from aircraft to cars. Hailed as a “modern 2JZ” thanks to its excellent performance and reliability, the B58 is used in several types of vehicles across BMW’s lineup, from sporty coupes to family SUVs. Some variants of this engine are also equipped with mild hybrid assistance, further boosting its efficiency.

BMW isn’t the only brand using the B58 in its vehicles: it also shows up under the hood of the Toyota GR Supra, famously the result of a collaborative project between Toyota and BMW, and the Ineos Grenadier.

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The B58 is a surprisingly adaptable engine and can provide varying levels of power to suit many different cars and powertrain combinations.

5 Cummins ISB

Maximum Power: 420 hp

Another entry flying the flag for diesel, the Cummins ISB is best described as large and in charge. With its 6.7-liter displacement and four-figure torque, it is designed to haul heavy loads of cargo, as well as powering large vehicles such as buses and trucks. These include the iconic yellow school buses that have transported American children for decades.

When it comes to smaller commercial vehicles, the ISB’s most well-known application is in the Ram 2500 HD, a staple of construction sites and other workplaces across the US. The ISB’s excellent towing and hauling abilities make it the perfect engine to power a heavy-duty truck that can tackle any task without breaking a sweat.

4 Mercedes-Benz M256

Maximum Power: 429 hp

Though not quite as extensive as BMW’s, Mercedes-Benz’s history with the inline-six also spans decades; the company built several straight-six engines between the 1920s and the 1990s. However, this changed at the tail end of the decade, with the M104 inline-six going out of production and a V6 being introduced to the lineup. In 2017, however, the inline-six made a comeback with the arrival of the turbocharged M256. The first model to be powered by the new engine was the E53 Sedan in 2019.

The M256 was packed with tech that made it a highly efficient, well-performing engine: this includes a small electric supercharger aimed at reducing turbo lag and a 48-volt starter/alternator system. Today, it’s used across a wide variety of Mercedes’ larger models in everything from the E-Class to the GLS-Class.

3 Jaguar Land Rover Ingenium AJ300

Maximum Power: 510 hp

The AJ300 first appeared on the market in 2019, four years after the Ingenium family of engines had been launched. The arrival of the Ingenium represented a shift for Jaguar Land Rover, which moved to building its own engines instead of sourcing them from Ford. Being a modular engine, the Ingenium is able to be built in a wide variety of layouts: the AJ300 is one of five different variants on the market.

It powers several Jaguar and Land Rover models, including the F-Pace, Defender, and multiple variants of the Range Rover. The AJ300 has been used as part of a mild hybrid or plug-in hybrid drivetrain, further increasing its efficiency. The Ingenium is a very high-tech engine, with clever bits of kit on board such as a 48-volt hybrid system, variable valve and cam timing, twin-scroll turbochargers, and an electric supercharger to reduce lag.

2 Stellantis Hurricane GME-T6

Maximum Power: 540 hp

No carmaker is immune from the downsizing trend, and amid pressure to reduce emissions and improve efficiency, many brands have looked into replacing V8 engines with six-cylinder alternatives. Stellantis is one such example, with the new Hurricane engine coming to replace the V8 (and, in some cases, V6) mills in several models from the brand’s large portfolio.

The twin-turbocharged Hurricane is available in various power outputs, starting with a 420-hp SO version and ramping up to 540 hp in HO form in models like the Ram 1500 RHO. It’s designed to deliver similar outputs to the V8 engines it replaced, but in a more efficient and environmentally-conscious way. While the Standard Output version is the most commonly spotted one, powering models across many of Stellantis’ brands such as Dodge, Chrysler, and Jeep (where it made its 2022 debut in the Grand Wagoneer), the High Output variant is expected to be used in selected high-performance models soon.

1 BMW S58

Maximum Power: 552 hp

At the very top of the list is the BMW S58, whose highest-output incarnation is the only inline-six on the market to break the 550-hp barrier (and the most power-dense engine ever built by BMW).

Based on the B58, the S58 adds some performance-boosting upgrades. Thanks to a shorter stroke, it can rev higher than the B58, and a series of mechanical improvements, such as forged internals, an electronically controlled wastegate, and an extra turbocharger, push the power output even further up. All this results in a 121-hp increase over the B58’s output. But not everyone can get the most powerful iteration of the S58, as it only achieves that 552 hp peak in the 3.0 CSL, limited to 50 units, and all already sold for huge sums of money.

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