Look around the auto industry and you’ll see a lot of the same types of engines, ones with four cylinders and a turbocharger. Turbo fours have emerged as the go-to engine for many manufacturers because they offer an excellent balance of efficiency and power. Many six-cylinder engines have been forced out of automakers' lineups because turbo four-pots can usually get close to the same if not better power and efficiency numbers than their six-hole counterparts.
The 2.3-liter EcoBoost four-cylinder engine in the Ford Mustang is a perfect example. It gets an EPA-estimated 21 mpg city and 30 mpg highway while still making 310 hp and 320 lb-ft of torque. It’s more powerful and more efficient than the V6 engine that Ford has long had in its base sports car. Now, Ford plans to kill the V6 model.
The Inline Six Doesn’t Get the Love it Deserves
One type of six-cylinder engine that’s been even more maligned than the V6 recently is the inline six-cylinder. A while back, inline sixes were common, but as time has gone on, most automakers moved to turbocharged four-cylinder engines. BMW clung to its straight six design for one main reason: it's exceptionally smooth. The design of an inline six-cylinder engine allows it to operate with very little vibration and noise.
There’s a myriad of reasons why this is, and we’re not going to get into all of the nitty-gritty, but we will touch on the basics. Inside an inline six-cylinder engine is basically three pairs of two cylinders and pistons. In each pair, when one piston goes up, the other goes down. This means the forces cancel each other out, which keeps the engine from shaking much or making any weird chatter noise. What you get is silky smooth power delivery and operation.
The lack of vibration and noise is the reason both Jaguar and Mercedes-Benz may return to the engine type in the future. That, and the fact that you can add turbochargers to an I6 and get loads of power.
Look to the BMW’s M240i (pictured above). The car has a 3.0-liter inline six-cylinder twin turbo engine making 335 horsepower. That launches the car from 0-60 mph in 4.2 seconds when equipped with all-wheel drive. It also gets 21 mpg city and 31 mpg highway. Surprisingly, that's more efficient and powerful than Ford’s four-cylinder EcoBoost Mustang. BMW has this engine in a number of models, including the new 5-series we recently drove. It is excellent in almost every way.
The Fate of the Inline Six Could be Good
With BMW doing great things with the I6 design, and Mercedes-Benz and Jaguar returning to the engine type, we wouldn’t be surprised to see more automakers move to put straight sixes in more of their cars. Turbo four-pots will still likely be the engine of choice for most automakers out there, but the I6 could become the go-to step up from there.
The engine type that might actually fade is the V8. While V8s will always have a special place in our hearts, we wouldn’t be surprised to see even less of them in the future. If automakers are able to get such great performance numbers out of inline six-cylinder engines and enjoy the low noise and vibration, the V8 may become a rare relic.