WE are entering a period in which the refiner is making a conscientious effort to give his fuel high antiknock value and such effective volatility that it will give superior performance in any automobile engine in which it is used. The present tendency is away from the misleading values such as color and gravity.
Ease of starting and good acceleration, particularly of a cold engine, demand high partial volatility even more than antiknock value, while the development of maximum power and a high fuel efficiency in modern engines supplying a large amount of heat to the mixture demand a relatively high end-point in the distillation test.
The author discusses the difficulties of using fuels possessing these characteristics in such engines, and indicates the desirability of the automotive and the oil industries cooperating in finding a solution of their joint problem of suiting the engines and the fuels to each other. The oil industry is now investigating the relation of vapor pressure, volatility, dew-point and similar fuel characteristics to engine performance, and we may expect within a short time to know what are the proper specifications for motor fuel to be used in engines that supply a large amount of heat to the intake manifold.
Various methods of improving motor-car performance, as by increasing the engine speed, the compression ratio, or the rear-axle ratio, and the effect these have of increasing the fuel consumption, are considered, and the conclusion is drawn that any further improvement must be based upon an increase in compression ratio.
Finally, comparison is made of the per-mile cost of using premium fuels and ordinary gasoline in engines of different compression-ratios. It is shown that there is no economic advantage in buying anti-knock fuels at a 3-cent premium, which now corresponds to about 15 or 16 per cent of the selling price, if an engine having a compression ratio of 5.5 to 1 can be operated satisfactorily on ordinary gasoline.