Editing Straight-six engine (section)

=== Europe ===
[[File:BMW M1 Ausstellungsmotor.jpg|thumb|1978-1981 [[BMW M88]] engine]]
[[File:Volvo S60 Polestar - T6 3.0l V6 turbo (MSP16).jpg|thumb|2014-2016 [[Volvo SI6 engine|Volvo SI6]] engine (transversely mounted)]]

Alfa Romeo's first production straight-six engine - 6.3&nbsp;L [[flathead engine|flathead]] petrol engine - was introduced in 1921 in the [[Alfa Romeo G1]] luxury car. An [[overhead valve engine|overhead valve]] design was introduced in the 1922 [[Alfa Romeo RL]] sports car, and an [[overhead camshaft engine|overhead camshaft]] design was used in the 1927 [[Alfa Romeo 6C]] sports car and various racing cars from 1927 until 1954. The last Alfa Romeo model using a straight-six was the 1961–1969 [[Alfa Romeo 2600]] executive car before the company switched to V6 engines.

Mercedes-Benz's history of straight-six engines began with the 1913 [[Mercedes D.I]] aircraft engine. The first automotive straight-six engine was the 1924–1929 ''Daimler M836'' 3.9&nbsp;L petrol engine.<ref>{{cite web |title=The Origin of the Mercedes 'W' Chassis Designation |url= https://www.thedrive.com/news/18783/the-origin-of-the-mercedes-w-chassis-designation |website=thedrive.com |date=27 February 2018 |access-date=27 December 2020}}</ref> Following World War 2, Mercedes resumed production of straight-six engines with the 1951 introduction of the [[Mercedes-Benz M180 engine|Mercedes-Benz M180]] overhead camshaft engine. In 1985, the [[Mercedes-Benz OM603]] 3.0&nbsp;L diesel straight-six engine was introduced. In 1996, the company replaced its petrol straight-sixes with a series of V6 engines, although it continued producing diesel straight-six engines. Production of petrol straight-six engines resumed in 2017 with the introduction of the [[Mercedes-Benz M256 engine|Mercedes-Benz M256]] turbocharged DOHC engine.

Opel began production of straight-six engines in 1927 with a 1.8&nbsp;L flathead petrol engine used by the [[Opel 8/40 PS]]. The displacement of this engine was expanded as it was used in later models such as the [[Opel Kapitän]] and [[Opel Admiral]], with later versions switching to an overhead valve (pushrod) design. In 1968, the straight-six versions of the [[Opel cam-in-head engine#Six-cylinder versions|Opel CIH engine]] were introduced, initially using a single overhead camshaft (SOHC) with some later versions using double overhead camshafts (DOHC). Production of the Opel CIH engine continued until 1993, when a V6 engine replaced it.

Volvo began production of straight-six engines with the 1929–1958 [[Penta DB]] flathead petrol engines. The company resumed production in 1969 with the [[Volvo B30 engine|Volvo B30]] overhead valve petrol engine, followed by the straight-six versions of the [[Volvo Modular engine#B6254FS|Volvo Modular Engine]] introduced in 1995 and then the [[Volvo SI6 engine]] introduced in 2006. Several models (such as the 1998–2006 [[Volvo S80#First generation (1998–2006)|Volvo S80]]) used the uncommon design of a transversely-mounted straight-six engine. Production of Volvo straight-six engines ceased in 2015.

BMW's first product was the 1917 [[BMW IIIa]] straight-six aircraft engine. The company began production of automotive straight-six engines in 1933 with the [[BMW M78]] petrol engine, a 1.2&nbsp;L overhead valve design that evolved over the years into the [[BMW M337]] (produced until 1958). Production of straight-six engines resumed in 1968 with the [[BMW M30]] single overhead camshaft engine, built for 27 years and used in various models. The 1978–1989 [[BMW M88]] engine was a double overhead camshaft design that was introduced in the [[BMW M1]] mid-engine sport car. BMW's introduction of turbocharged straight-six engines (aside from the low-volume variants of the M30 engine in the 1980s) was in 2006 [[BMW N54]] and the production of naturally aspirated engines ceased in 2015. {{as of|2022}}, the [[BMW B58]] turbocharged straight-six engine remains in production,<ref>{{cite web|last1=Murphy|first1=Tom|title=Seven Turbos, Three Hybrids Share Wards 10 Best Engines Honors 2017 &#124; Wards 10 Best Engines|url=http://wardsauto.com/2017/seven-turbos-three-hybrids-share-wards-10-best-engines-honors|website=WardsAuto|publisher=Penton|access-date=24 May 2017|date=12 December 2016}}</ref> along with its higher performance [[BMW S58]] variants.