Soon after Caterpillar Tractor Co. was formed in 1925, Chairman C. L. Best began receiving pressure from Dealers and customers to quickly create and release a diesel engine that could be used to power tractors. He replied, “When the diesel tractor is ready, Caterpillar will have it.” A special research team spent more than four years on research and required an investment of more than $1 million to develop Caterpillar’s first diesel engine, the D9900, which went into production in October 1931. It weighed 5,175 pounds, developed 86.8 horsepower at 700 rpm, and was designed to power Caterpillar’s first diesel tractor, the Diesel Sixty. The D9900 engine model was the world’s first mass-produced diesel engine to be developed, manufactured, and applied as a power plant in a mass-produced vehicle.
“Caterpillar’s first diesel engines gave customers an engine that could do they work they needed, higher production at a lower cost. These engines had 18-1 compression compared to 10-1 for the gasoline engines, the cost per hour of diesel was less than gasoline, and in a pinch they could burn just about any type fuel.”
Wayne Evans, Sr., Yancey Bros. Co.