GAS MILEAGE VIA ENGINEERING

Of course, only a fool would believe that after 114 years of internal combustion engine development there is still room for a 40% improvement, and in only 6 years at that. But the PR-men didn't exactly say that, and on digging a little, one finds that there is a little improvement possible by pure engineering, much more by various subterfuges, and most by tactics in-between.

In pure theory, the gas mileage of a car with given weight and power could be drastically improved by devices that do not violate any physical laws, but that have not yet been invented. Typically, the energy wasted by a decelerating car as heat in the brake linings could instead be stored for future use

in an electric battery, or an air compression tank, or a spinning flywheel, for example. A contemporary battery could not absorb the discarded energy fast enough, but other devices could. However, all three are at present so heavy that the fuel consumption for carting them around would more than offset the savings, and there is no great breakthrough in energy storage and recovery (or other such desirable method) now on the horizon.

One can also go for the smaller, but attainable rewards; such as decreasing warm-up time, which is wasteful of fuel, by reducing the amount of oil in circulation until the engine is warm; or reducing friction in the gears; or reducing the rolling resistance of the tires; or reducing aerodynamic resistance. Naturally, this involves difficult tradeoffs: Bald tires have half the rolling resistance of new ones, but economy would be traded for safety; and aerodynamic streamlining usually increases the body weight and soon becomes self-defeating for fuel economy. [More: MIT Technology Review, Spec. issue, Feb. 1975.]

Not much, then, can be done for cars of given weight and performance; but there is a lot of mileage to be gained by simply reducing both. There are, first of all, possibilities of reducing unnecessary weight. For example, General Motors pioneered the all aluminum engine block for the Vega by an electrochemical etching process leaving aluminum with a high silicon content as the wearing surface, and the other companies are now following suit with comparable methods ("sticking" steel cylinder linings into the block, since steel and aluminum cannot be welded to each other).

The imports, on the other hand, simply cut weight by making the car smaller and giving it a smaller engine; the mileage is higher, but at the expense of performance (and safety). The little Honda gets over 50 mpg; and if you walk, you make a mile on no gas at all.

Then comes the transition from engineering to politics. A lot of weight (30 to 40 lbs) can be saved by omitting the spare tire, a possibility considered by Detroit at one time and rejected for obvious reasons. But perhaps not for good: A tire which remains operable for some time after a puncture is on the way.

Another trick in this class is saving weight by making the gas tank smaller, thus reducing the range of the car. Chrysler knocked off a precious 12 lbs from its Feather Duster by reducing the gas tank capacity from 14 to 12 gallons.

By such tricks, some clever and clean, some clever and shady, Detroit has improved the mileage on some models by as much as 25%.

But 40%? Only by tricks that are very shady.