Straight-six engine

A 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 gradually became more common in the 1970s and by the 2000s, V6 engines had replaced straight-six engines in most light automotive applications. Due to their high and smooth torque, simplicity and reliability, weight and space, and balanced power delivery, straight-six engines are a common power source for trucks and buses.