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Buick named their six-cylinder cars "Buick 6" from 1916 through 1924, and in 1925, divided them into Standard 6 and Master 6. The Master 6 was renamed Series 121 and 129 in 1929 and Series 40 in 1930. All were powered by a Buick Straight-6 engine, with multiple body styles, and starting in 1926 used the newly established GM B platform, which it shared with Oldsmobile. Although Buick produced mostly four-cylinder cars in the teens and early '20s, as it had been doing, the new six=cylinder cars became more common. Buick first made six-cylinder cars in 1914, with a 331-cubic-inch engine, which was originally a racing engine, later used in limited production as the Series 50. The 331 engine was dropped in 1916 and replaced with the much smaller 40 series engine, starting with a 224-cubic-inch in 1916 and 1917, the 242 engine from 1918, increased to 255 in 1924, increased again to 274 for 1926 through 1928. The engine was increased again to 309 for the Series 121 and 129 in 1929 and Series 40 in 1930, after which all six-cylinder engines were suddenly dropped and all models of Buick were equipped with the legendary Straight 8, starting in 1931 and for decades thereafter.