There are actually 2 compressed air engines that look good. The French engine is going into production, and is basically a piston engine that doesn't use combustion, just pressurized air. The second Australian engine is a rotary, that uses compressed air for rotation and 'lubrication'. This engine is small enough to easily pick up with 2 hands, and it uses no gear box, putting around 90% of its power output to move the vehicle. The initial design was intended for small warehouse vehicles moving produce, but it has been tested in at least one car. Anyone notice the news today that the Saudis are now thinking gas prices are "abnormally high", and might reconsider increasing output?