The document discusses the six-stroke engine, which adds an additional power stroke compared to traditional four-stroke engines. It provides a brief history, describing how the concept was introduced in 1883 but the design did not fit automobiles until more recent inventions like the Bajulaz engine in 1989. The key features of six-stroke engines are described as increased efficiency, torque, and reduction in fuel consumption and pollution compared to four-stroke engines. Examples of different six-stroke engine types and designs are provided, along with their advantages and potential applications, particularly for automobiles where it could significantly reduce fuel use and emissions.