The advent of oil engines by the start of the 20th century, suggested a change on the horizon. From Froelich's first tractors to Hart-Parr products, oil tractors seemed the way ahead. Case hired Joe Jagersberger, and he tested a motor by racing in the 1911 Indianapolis 500. Case began production of the 30-60 oil engine in 1912. Case also produced kerosene tractors in the teen years, similar to the Rumely oil pulls. During World War I, Case's sales and demand grew dramatically in Europe. These increases were directly connected to the war; as many farm laborers became soldiers, each remaining farmer needed to become more productive, and machinery was the way to make this happen.