There was room for improvement in 1970s automobiles — but not because of any “suppressed carburetor.” Fuel injection and computer control of engines improved efficiency by a few percent. Radial tires, because of less rolling resistance, helped by a few percent. So did improved aerodynamics. Lock-up torque converters on automatic transmissions, again, provided a few-percentage-point improvement. Front-wheel drive, by reducing energy losses to the rear wheels, helped. Increasing the number of gears in transmissions, so that you could always operate the engine in its most efficient RPM range, ditto. Reducing overall vehicle weight probably helped more than all these others combined; the average American sedan weighs much less today than it did in 1973. Each of these improvements in automobiles was individually tiny and often achieved with an enormous investment of capital. None of them was something that you could put together in your garage.
There are areas where individuals can tune automobiles to make them more efficient. Automobile makers are required to guarantee to the federal government that their entire fleet will meet federal emissions standards for many years. As a result, they must tune automobiles to make sure that only a tiny percentage will go off the ragged edge. Individual shops can, and sometimes do, reprogram the engine control computers to get a bit more gas mileage or horsepower — while still meeting emissions standards. But then again, they can verify that doing so hasn’t taken this particular car outside the emissions limits. Still, these are minor improvements; not 200 miles per gallon.
When I see these bizarre claims of suppressed systems that you can build yourself to run your car on water, I just shake my head in amazement that anyone would seriously think this possible. There are definitely some areas where clever engineers can come up with major improvements. Bruce Crower, for example, is developing something called the six-stroke engine — which injects water into a gasoline engine cylinder after the gasoline vapor has driven the piston. It uses the waste heat of the cylinder to produce steam, which drives the piston one more time. It’s a clever idea and might actually turn into something serious one of these days, because it both uses less gasoline and substantially reduces the need for an engine cooling system. But no one is suppressing it and it isn’t something that you can just throw together in your garage.
Conspiracy theories are very popular, in politics, in religion, and even in automotive technology. At the core of the “run your car on water” conspiracy theory is the belief that you can get something for almost nothing. Think of it as socialism for automobile engines!