The document discusses a six stroke engine, which has two power strokes compared to the one power stroke of a conventional four stroke engine. It works by using the heat from the four stroke cycle to power an additional expansion and exhaust stroke. This extracts more energy and improves efficiency over a four stroke engine. The six stroke engine requires modifications like a divided fuel/water tank, thermal resistant materials, a modified camshaft, and a water injector system. Analysis shows lower fuel usage, reduced emissions, and up to 50% higher thermal efficiency compared to a four stroke engine, but it also has limitations like cold starting issues and higher manufacturing costs.