No Thanks...4 Stroke For Me Please!

Check this link out if you want info on a different type of engine...Stirling engine, hmmm. Interesting, but Ill keep my 4 stroke.
http://travel.howstuffworks.com/stirling-engine1.htm

Look into the Carnot cycle for the most efficient possible variant of the concept of heat engines.

I've been told (but I don't know if it's true) that DAF's first prototype cars used stirling engines, the best point about these engines is that they can burn anything.