Written By Larry Gay
The earliest farm tractors ran on gasoline, but kerosene soon replaced gasoline as the more popular fuel. Distillate, also known as tractor fuel, became popular during the late 1920s and the 1930s. Also diesel engines began to be used as a power source for crawler tractors in the early 1930s. In 1935, International Harvester introduced the McCormick-Deering WD-40 and advertised it as "America’s first diesel-powered wheel tractor." This made the McCormick-Deering WD-40 a tractor trendsetter.
The WD-40 was a combination of the standard-tread W-40 tractor and the diesel engine from the McCormick-Deering TD-40 TracTracTor crawler. The WD-40 was rated as a 4-plow tractor with 44 belt horsepower and 28 drawbar horsepower. There was a choice of steel wheels with a variety of lugs or rubber tires. A PTO and lights were optional. Harvester advertised the WD-40 operated on diesel fuel which cost less than gasoline or kerosene and used one-third less fuel than a gasoline engine with the same horsepower.
This International diesel engine had four cylinders with a 4.75-inch bore and a 6.50-inch stroke which resulted in a 460-cubic-inch displacement. It started on gasoline and then switched to diesel after the engine was warm. The way IH accomplished this resulted in a unique appearance for the engine. The left side looked like a diesel engine with an injection pump and four fuel lines. However, the right side looked like a gasoline engine with a carburetor, magneto, and spark plugs. Each cylinder was equipped with an auxiliary combustion chamber which was used for the gasoline operation. After the engine was warm, the auxiliary chambers were automatically closed and then the engine operated with diesel fuel in the regular combustion chambers.
During 1940 and 1941, the number diesel-powered wheel tractors on the market expanded with the introduction of the Oliver 80, the Farmall MD, and the McCormick-Deering WD-6 and WD-9 tractors. Diesel engines for farm tractors began to become more popular for the large standard-tread tractors by the 1950s, with some powered only by diesel engines. By the mid-1950s, most tractor manufacturers offered a choice of diesel, gasoline, or LP-gas for their row-crop tractors, especially the larger models. Diesel engines started becoming available for utility tractors by the end of the 1950s. Today all farm tractors are powered by diesel engines as the last gasoline-powered tractor tested at Nebraska was the International 284 utility tractor in 1978.
Larry Gay is the author of four farm tractor books published by the American Society of Agricultural and Biological Engineers, including Farm Tractors 1975-1995 and Farm Tractors 1975-2005. The four books may be obtained from ASABE by calling 800-695-2723.