I would guess somewhere between the Aerocivic (80mpg) and the VW 1 Liter (235mpg). Split the difference and decrement the results some for what I assume to be a much larger (than the 1 Liter) vehicle. Maybe 130mpg? Just so you know, the Aerocivic uses barely any power when cruising... less than 15hp at 75mph if you don't include any parasitic power (headlights and such). If you only had a need for 30hp, you might get by with a much smaller than 400cc engine... what does a 250cc engine put out?
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