This article relies largely or entirely on a single source. (May 2019)
The Cadillac Model Thirty is an automobile that was introduced in December 1909 by Cadillac, and sold through 1911. It was the company's only model for those years and was based on the 1907 Model G. The 1912 Model 1912, 1913 Model 1913, and 1914 Model 1914 were similar but used larger engines.
The 1910 model was available with a closed body, the first time a US automobile manufacturer had offered this type.
The engine was the same 226.2 in³ (3.7 L) four-cylinder L-head design used in the Model G, and that car's simple sliding-gear transmission was also adopted. The engine was bored out to 255.4 in³ (4.2 L) for 1910 and 286.3 in³ (4.7 L) for 1911 and 1912. The engine was reworked, with a longer stroke, for 1913, giving 365.8 in³ (6.0 L) of displacement. This same engine served in 1914.