Here is an industrial film, produced by Shell Oil, in which the history of the Diesel engine is described. A goodly amount of the movie's length is devoted to discussing the various types of engines in use almost three-quarters of a century ago, but I'll be honest with you (as I always try to be): I have no clear idea of how these operate. I know that auto Engines use a four-stroke cycle, while Diesel engines seem to use only two. However, looking at the animated drawings of these engines in operations brings me no understanding, nor do the words.
What is clear is the message of the film: use Diesel engines, which are far more efficient! And buy diesel fuel, which, coincidentally or not, is sold by Shell.