Straight-six engine

The straight-six engine (also referred to as an inline-six engine; abbreviated I6 or L6) is a piston engine with six cylinders arranged in a straight line along the crankshaft. A straight-six engine has perfect primary and secondary engine balance, resulting in fewer vibrations than other designs of six or fewer cylinders.

Until the mid-20th century, the straight-six layout was the most common design for engines with six cylinders. However, V6 engines became more common in the 1970s. By the 2000s, V6 engines replaced most straight-six engines.