In 1936 a Canadian man called Pogue achieved 200mpg in a five litre Pontiac. Surely with modern technologies this could be achieved or even surpassed, rather than the comparatively obscene fuel efficiencies currently displayed?
The restrictions to building such a device are more social, political and financial than technological. For example, such a vehicle would cause huge changes to the volume of oil used and its price.
Pogue’s invention was so scary that it threatened to collapse the Canadian stock market. He mysteriously disappeared, only to turn up a year later running a parts company; his family refused to be drawn on details. Surely we can achieve results that match or surpass Pogue’s?