Improving on an already good concept
Check out
this design for a new diesel engine. It's a two cylinder, opposed piston, opposed crankshaft design. The design is usually found in large diesels (locomotive and ship size, usually made by Morse Fairbanks and Cooper Bessemer), but it has been compacted into a unit that weighs 275 lbs and produces 325 HP. Just think about that power to weight ratio. An engine like this in a hybrid car would attain a fuel economy of at least 120+ mpg.
P.S. Bradford Degen got laid