This is good ideas, but I already have a statment not mainstream. No 3 wheels, no two wheels, must be four wheels, realistic for highway (I saw jay leno flying down the road in the aptera..)
My ecomod started with a monte caro SS and 2.73 gears..24+ mpg was great. that was v8 and 3500 pounds. I grew up around tractor trailers at 5 mpg...but hauling 40 tons the goal.These 3 wheeled and less and 500 pound vehicles could have the worlds dumbest engine with a total weight of 500 pounds to push..that is not the real worldly challenge.
My latest in common sense is internals and 87 octane put together correctly is the 3 main boxer engine is the one that even comes close to hypermilers goals and real vehicles.real weight, rela crosswinds and real tractor trailers on the same real roads.
I could add what I learned about that, its been 12 years, 2wd,4wd,sedan ,wagons, dual range and single, tall gears and short. carbed and injected...there is a miraculous combo...It is never what most think, and that is my loneliness.
Whatever the forum does, it will be interesting to follow and learn.