Which one is more efficient? A four stroke engine or a two stroke and why?
This depends on what type of efficiency you are referring to. As far as power generation, two-stroke by far. Simply because it accomplishes in two strokes, what a four stroke motor takes twice as long to accomplish. Fuel consumption is a different story. Four strokes are more efficient because there is separation of fuel and engine oil, as well as intake and exhaust gases, leading to less pollution, and better mileage. Hope this helps answer your question somewhat.
