Inlinesix

An inline-six, also known as a straight-six, is an internal combustion engine configuration with six cylinders arranged in a single straight line along the crankcase. The cylinders share a common crankshaft and are typically aligned in a vertical orientation within the engine bay.

Inline-six engines are renowned for their smooth operation. The configuration is inherently well-balanced, with primary and secondary forces largely canceling due to the even spacing of the cylinders and the continuous crankshaft arrangement. This results in low vibration and refined characteristics, a trait often associated with brands such as BMW, Jaguar, and Mercedes-Benz.

Advantages of the layout include strong mid-range torque, good high-rpm performance, and a compact crankshaft design relative to an equally displacing V6. Drawbacks include a longer engine block that can complicate transverse mounting in front-wheel-drive layouts and potentially higher manufacturing costs. The long shape also influences packaging and weight distribution in some vehicle platforms.

History and usage: Inline-sixes have been common in mid-20th-century European cars and later in many luxury sedans, sports cars, and trucks. Notable manufacturers with long-running I6 programs include BMW, Jaguar, Mercedes-Benz, Volvo, and Toyota. Modern I6 engines often feature technologies such as direct injection, turbocharging, and mild-hybrid systems to improve efficiency and performance.

Examples and variants: Notable inline-six engines include BMW’s M54 and turbocharged B58, Mercedes’ newer I6 families, Jaguar’s AJ family, Volvo’s B6304 series, and Toyota’s legendary 2JZ-GE/GTE engines. While some markets increasingly favor V6 or four-cylinder equivalents for packaging reasons, the inline-six remains prized for smoothness and refined character in suitable applications.