The design was popularized in pre-war aircraft, and now, it’s diving headlong into the future.

The first BMW inline-six engine climbed skyward into the shadow of war. By the late summer of 1917, conflict had clawed at Europe for half a decade. Escalations in air-to-air combat were shifting the future of warfare. Each combatant knew that building light, powerful, and reliable airplane engines was of national importance...

...Refinement, torque, and a sense of occasion can still be had. Modular sixes based on those four-cylinders are coming into vogue. Jaguar Land Rover unveiled its new straight-six last year. GM just introduced a new 3.0-liter diesel inline-six for half-ton truck applications, returning to a segment where Ford and Chrysler have chosen to offer vees. And old stalwart Mercedes, after closing eight decades of continuous inline-six service in 1999, returned in 2017 with one of the most forward-looking examples of a straight six ever built.