Straight-five engine

The straight-five engine (also referred to as an inline-five engine; abbreviated I5 or L5) is a piston engine with five cylinders mounted in a straight line along the crankshaft.

Although less common than straight-four engines and straight-six engines, straight-five engines have occasionally been used by automobile manufacturers since the late 1930s, particularly the Mercedes Benz's diesel engines from 1974 to 2006 and Audi's petrol engines from 1979 to the present. Straight-five engines are smoother running than straight-four engines and shorter than straight-six engines. However, achieving consistent fuelling across all cylinders was problematic prior to the adoption of fuel injection.