This booklet provides a semi-technical explanation of how Diesel motors work and how they differ from gasoline engines. For example, it explains the difference between a two-cycle engine and a four-cycle engine using the metaphor of a passenger train: in a two-cycle engine (such as a Diesel), passengers board one end of the train as other passengers get off the other end; in a four-cycle engine (such as the gasoline engines used in most cars), all passengers get off before new passengers are allowed on.
Oddly, the first two pages are the story of “the mysterious disappearance of Rudolph Diesel” in 1913. The story hints that he might have been murdered by the German government because he “knew too much.” However, the end of the story reveals that Diesel was broke because he was unable to make a profit from his invention. The unwritten message is that Diesels might have been invented by a German, but it took an American company to make it commercially successful.
This is apparently what passed for “public relations” for General Motors in the late 1930s. The booklet is copyright 1939, which means it was probably first distributed at the 1939 New York World’s Fair. But this is the third printing and a date in back says May, 1940–the 1939 fair continued in 1940. Of course, the outstanding exhibit of that fair was the General Motors Futurama ride, which would have overshadowed anything about Diesels.