ECONOMICAL RUNNING.
[To the Editor cf 'hit SPECTATOR.] Sia,—Lord Montagu of Beaul:eu's article on petrol consump- tion in a recent issue of the Spectator encourages me to ask a question to which the answer is probably quite simple, but which continues to puzzle mc. Suppose two cars accom- iilishing a specified journey, one at forty miles per hour
the other at twenty. Lord Montagu of Beaulieu tells us that the consumption of petrol in the first case will be greater, but how is it that the double time during which the petrol is flowing in the second case does not bring things level ? I should be grateful if he, or some other motorist, will solve my difficulty.—I am, Sir, &c.,
H. SAYERS.
[Lord Montagu of Beaulieu writes in reply :—" The reason for the greater consumption of petrol at the higher speed is that greater wind resistance and friction of working-parts absorb more power, or in other words mean a greater consumption of motor spirit. The greater suck on the jet at high engine speeds pulls more motor spirit through it, and therefore increases the consumption. Any motorist can test for himself the most economical speed of his own particular type of car, which is generally about two• thirds to three-fifths of its maximum speed. For instance, a car with a maximum speed of thirty m.p.h. would probably be most economically run at twenty m.p.h."—En. Spectator.]
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