Welcome aboard, David.
To build interest here, might I suggest you start by posting the equations you've developed that project 200+ MPG?
I seem to recall a series of formulas showing that a one ton car, driven by a 100% efficient engine and accelerating very slowly, could manage about one light-second per gallon in intergalactic space.
But here on earth, things work a bit differently. A "super economy device" that would allow a typical street-legal vehicle -- driven in a practical manner by Joe Average -- to achieve 200+ MPG would be an astounding achievement.
So, share your math.
Rick