Looking at the market, VW has built the VW XL1 (EN, DE), a hybrid car with up to 260mpg. The german site says there was a test drive on the street where the car indeed consumed 0.89l diesel /100km, which equals 240mpg. But there are also many other confusing numbers, giving up to twice the consumption. I also find 1.82 l/100km with full and 1.94l/100km with empty battery. The last value is what you get when you feed the car by fuel only, and corresponds to 125mpg.
So yes, in general, it is possible to build a car with 100mpg or better.
But this car is only 1.6m wide and 1.1m high, with two seats one behind the other for best aerodynamics, weights just 750kg and 40hp. Oh, and it's a diesel, with an in general lower consumption.
A more reasonable car like the Tesla Model S weights about 2000kg, which is similar to the weight of Tom Ogle's Fort Galaxy. And it runs 260 miles on a 75kWh charge (EPA).
Gas contains 125MJ/gallon=34.7kWh/gallon of energy, so if the Tesla would burn gas to generate electricity at 100% efficiency, it would consume 75/34.7=2.61gallons for 260 miles, i.e. exactly 100mpg!
But a combustion motor has a theoretical maximum efficiency of 40-50%, because the exhaust gases are hot and still under pressure when leaving the cylinder. In reality, internal and drive train friction lower the efficiency even more.
Even electric cars with their >90% efficiency motor do a lot to increase their "milage". For example, the kinetic energy of the car is used to charge the battery when braking, instead of wasting it as heat.
Replacing the carburetor by a system which allows to add the fuel more controlled, more precisely and in a ways that allows a better, more complete combustion can increase milage a lot, but 100mpg by just this is far from realistic.