The inline-six engine is among the best cylinder configurations in the motoring industry, heralded as one of the smoothest and most refined ways to propel a motor vehicle. Because of the ease of driving, the straight-six is the configuration of choice for luxury brands – with BMW specializing in making the absolute best models.
The straight-six was the next logical step after the inline-4, with the Dutch manufacturer, Spyker, debuting a version of this engine in their 60-hp racecar in 1903. Inline-6s increased in popularity by 1909 and became the configuration of choice for most automakers around the world. It was only in the 1950s when V6 engines began taking over thanks to their more compact dimensions. Interestingly, the straight-six engine configuration is making a comeback, with Chrysler, Jaguar, Mazda, and Mercedes-Benz replacing their V6s for straight-sixes.
The straight-six is a fantastic engine and many manufacturers have produced some amazing motors over the years that everyone should have a go in. Here are ten inline-six engines every gearhead should try at least once in their lives.
10 Cummins 6.7 ISB
The Cummins 6.7 ISB is the turbo-diesel engine of choice for the RAM 2500 and bigger pickup trucks, available in the US. Unlike the 6.6-liter Duramax in the Chevrolet Silverado 2500 and the 6.7-liter Power Stroke in the Ford F-250, the 6.7-liter Cummins is a straight-six as opposed to the V8s in the rivals.
The Cummins produces a maximum power output of 400 hp and an incredible 1,000 lb-ft of torque – pretty much on par with the other two. This is definitely an engine that motoring enthusiasts need to drive at least once – mostly to experience the mountain of torque.
9 BMW B57
From one diesel on to the next. BMW creates among the best turbo-diesel straight-sixes on the market and the current B57 is one of the best. Available in either single or twin-turbo versions, the B57 is available in the 30d, 40d, M40d, and m50d models.
The 3.0-liter unit produces between 260 and 400 hp, with torque ranging between 450 and 560 lb-ft. The B57 is a fantastic engine able to outrun most normal sports cars as well as being smooth and efficient during town driving. Sadly, BMW discontinued the quad-turbo version in 2020.
8 Ford Barra
Australian automakers are mostly rebadged versions of other manufacturers, with FPV and Holden using Ford and Chevrolet vehicles and parts. Interestingly, Ford of Australia did create their own powerplant in the form of the absolutely brilliant Barra inline-6.
The Barra was available in the Ford Falcon between 2002 and 2016 and came in either naturally aspirated or turbocharged forms. The Barra is an engine on par with Toyota’s 2JZ and Nissan’s RB26 in terms of tunability – with some Barras producing supercar levels of power.
7 BMW S54
The BMW S54 is considered by many to be the last true M3 engine as it featured all the trusted hallmarks of a BMW M-engine – 6 cylinders, independent throttle bodies, and an exhaust note quite unlike anything else on the market.
The S54 displaced 3.2 liters and produced 338 hp and 269 lb-ft of torque. The S54 only featured in the E46 M3, with no direct successor as the E92 M3 went with the S65 V8. The F80 M3 did return to the straight-six configuration, but the S55 gained two turbos and a heap of power.
6 Mercedes-Benz M198
The Mercedes-Benz M198 may not immediately stand out as a memorable straight-six, but it made an impact under the hood of the 300SL Gullwing. The 3.0-liter unit came out of the company’s family sedan of the time but transformed the 300SL into a proper sports car.
The M198 produced 240 hp and was one of the first production engines with mechanical fuel injection – resulting in better power figures and reliability. The M198 rocketed the 300SL to a top speed of 163 mph – the fastest production car of the time.
5 BMW M88
The BMW M88 straight-six was the engine of choice for the legendary M1 racecar. It was specifically designed for the car, but due to the situation surrounding the M1, it never really had the chance to stretch its legs – so to speak.
The 3.5-liter unit produced 273 hp in the M1, but BMW repurposed the M88 – with some modifications – to other BMW models such as the E28 M5 and E24 M635CSI. The SOHC version of the M88 was also used in the E12 M535i – the precursor to the M5.
4 Jaguar XK6
The Jaguar XK6 engine is the motor of choice for one of the most beautiful cars ever made – the Jaguar E-Type. The E-Type launched in 1961, but the XK6 straight-six harked back to 1948, as Jaguar designed and built the 3.4-liter DOHC engine for the XK120.
Fast-forward to the E-Type and the engine grew to 3.8 and 4.2 liters, with power up to 220 and 265 hp respectively. The XK6 engine produces one of the best exhaust notes of any straight-six, with the Eagle Speedster’s enlarged 4.7-liter version accentuating the 1960s.
3 Nissan RB26DETT
The Nissan RB26 is one of the most loved engines on the planet. Introduced in the R32 Nissan Skyline GT-R, the RB26 was soon nicknamed ‘Godzilla’ and it continued to receive updates through the R33 and R34 GT-Rs.
Today, the RB26 has a huge following and there are many swaps done to Nissan models to get the RB26 into it. The main reason why the RB26 is so popular is the fact that it can easily be tuned to an absurd amount of power – all while spending a small amount of money. It is also famous for its part in the third Fast & Furious movie, where it was used to make a Ford Mustang go sideways.
2 Toyota 2JZ-GTE
Like the RB26, Toyota’s 2JZ has a following – but much larger and more aggressive. Toyota introduced the 2JZ with the twin turbos in the A80 Supra, where it officially stayed below the Japanese Gentleman’s Agreement of 276 hp – even though it pushed well over 300 when dyno’d.
Toyota knew the community would want to tune the engine, so they built it in a durable manner, meaning a quick tune can see more than 500 hp, using stock parts. This gives the 2JZ near unlimited tuning potential, able to out-drag anything from an A90 Supra to a Bugatti Veyron.
1 BMW S58
The BMW B58 and its M-Division version – the S58 – are often called the 2020s version of Toyota’s 2JZ-GTE. The reason behind this is that the B58 features in the A90 Supra, but also because the engine is just that good. While BMW states that the S58 in Competition form produces 510 hp, the actual figure is well above that.
The tuning potential is also quite great, with the engine capable of some pretty impressive things thanks to the heavier-duty internals. Manhart and Alpina have already gotten over 600 hp out of the S58 and B58, showing that it is an engine that means business. Tuned or not the S58 is an engine to have a go with.