Which automaker developed the first mass-produced V8 engine?

Cadillac developed the first mass-produced V8 engine.

Cadillac’s pioneering V8 was the Type 51, introduced in 1914 for the 1915 model year. It was a 90-degree, water-cooled, side-valve engine with a 314-cubic-inch displacement. Cadillac’s production methods allowed the V8 to be offered in substantial numbers, making it the first road-going V8 mass-produced in significant quantities.

That distinction does not mean Cadillac invented the V8 itself. Earlier V8s existed, including aviation engines and experimental or very limited-production automobile engines. Rolls-Royce built only three V-8 cars in 1905, while the French manufacturer De Dion-Bouton produced V8 engines before Cadillac’s breakthrough. Cadillac’s achievement was bringing the configuration into large-scale automobile production.

The Type 51 also helped establish Cadillac’s reputation for technical innovation. Later Cadillac V8s introduced refinements such as improved crankshaft design and, eventually, overhead-valve layouts. Chevrolet later built the first American overhead-valve production V8, but Cadillac holds the mass-production milestone.