Cummins' Auburn: 40+ MPG In 1935

The Hemmings blog posted this very interesting article about the early efforts of diesel engine manufacturer Clessie Cummins to convince the automotive industry of the efficiency of diesel engines.  He had a very simple formula.  Take one 1934 Auburn, one of the more upscale cars available at the time, put in his own special diesel engine, and drive it across the country. 

In June 1935, he debuted the result of that effort: a 1934 Auburn powered by an experimental Cummins Model A six-cylinder diesel. Where all of Cummins’s previous diesels used cast-iron engine assemblies, the Model A had an aluminum block and head, “making it more comparable in weight to a gasoline engine,” according to Cummins company literature. A Time article announcing the Cummins-powered Auburn noted that the Model A, which developed 85 horsepower from 377 cubic inches, weighed 80 pounds more than the Lycoming straight-eight that originally powered the Auburn (870 pounds total). Combined with a three-speed manual transmission and a two-speed rear axle, the 4,000-pound car was able to pull down 40.1 MPG on the first leg of a NY-to-LA transcontinental trip that Clessie planned to display the economy of the Model A engine. The trip, which lasted from June 17 to July 4, covered 3,774 miles and consumed just $7.63 worth of fuel; assuming the same fuel cost quoted in the Time article (and assuming my math is correct), that translates to an average of 44.5 MPG over the entire trip.

One of the interesting points in this article was the fact that, prior to 1932, the trucking industry did not use diesel engines.  It was the reliability and endurance of a Cummins powered race car at the 1931 Indy 500 that convinced Kenworth to offer a diesel engine the following year as an option.  The rest is history.