High Quality Content by WIKIPEDIA articles! The Mercedes D.IV was an eight-cylinder, liquid-cooled inline aircraft engine built by Daimler Motoren Gesellschaft (DMG) and used on a small number of German aircraft during World War I. The design was based around the pistons of the ubiquitous D.III 6-cylinder design and developed 162 kW (217 hp), making it a Class IV motor under the classification system then in use in Germany. When the reliability of the engine proved disappointing, it was supplanted in production by the unrelated six-cylinder Mercedes D.IVa. Specifically, the long crankshaft used in extending the original straight-six design to a straight-eight proved susceptible to breakage.