A straight six engine, also known as an inline six engine, is an internal combustion engine with all six cylinders mounted in a straight line, and with a common crankshaft. Often abbreviated as "I6" or "L6", this configuration is the simplest one to possess both primary and secondary engine balance, which means it has far less engine vibration than designs with fewer cylinders.
Engines of this type do have disadvantages of length, and of the stresses placed on such a long crankshaft.