PETROL ECONOMY

Hawera Star, Volume LI, 20 June 1931, Page 12

PETROL ECONOMY

VALUE OF CAREFUL DRIVING. Few motorists appreciate in full the important influence which speed and driving methods in general exert upon the amount of petrol consumed. Naturally extreme economy involves a sacrifice in motoring comfort which few drivers countenance, but, on the other hand, many people are certainly wasting petrol in ways which they could easily correct without appreciable loss of time or profit. Many persons believe that, although fast travelling requires greater power, this is compensated by the rapidity with which the journey is covered. In this way they seek to prove that the petrol consumption should not be markedly affected, but such an argument is quite fallacious. At any speed above 30 m.p.h. wind resistance and the power to overcome it botli increase very rapidly. means that the higher the speed the wider must the throttle be held open. The throttle, of course, acts merely as a tap regulating the amount of mixture drawn into the engine. In reasonably level country the number of revolutions which the engine makes is exactly the same whether the distance he covered slowly or quickly. From this argument it is. clearly seen that, as the faster journey involves a bigger throttle opening, the petrol consumption will necessarily be higher. If practical proof in this connection he needed it may he mentioned that in a series of tests carried out in England recently, it was shown that the mileage per gallon at 2Q m.p.h. and 30 m.p.h. was practically the same, but that at 60 m.p.h. it was halved. These results may he slight y modified in very hilly country, because a ‘ higher average speed may enable certain gradients to he taken with a rush in top gear which would otherwise have necessitated changing down. Naturally, the use of a lower gear increases the engine speed and more petrol is consumed. It is, of course, had practice to allow an engine to labour pulling the car slowly uphill in “top.” but, all the same, too frequent use of the gearbox causes an unnecessary waste of fuel. The careful driver must endeavour to strike a happy medium between these extremes. The next point is that the speed should be kept as steady as possible. The driver who is constantly accelerating up to 60 m.p.h.. immediately afterwards having to brake heavily for a corner or other traffic, uses lar more petrol than one who is content to plug along at more modest speeds. This is simply due to the fact that the power needed to accelerate the mass of the car is much greater than that required to keep it running at a steady rate. , , . , Petrol also is wasted by a jerky action of the foot on the throttle. In some cases throttle springs are unduly j light, so that on a rough road it is difficult to keep the foot stendv withI out some of rest. An English expert stated recently that it is a great pitv that people do not make greater use of the hand throttle, control, because a steady setting is far more economical than one which is constantly varying. When cruising on a main road it will usually be found that-, baling attained tbo speed required, the throttle can be closed slightly without losing headway. Use of the minimum throttle | opening is economical.