THE PRICE OF PETROL

Press, Volume LXXIV, Issue 22305, 20 January 1938, Page 8

THE PRICE OF PETROL

TO TH* EDITOR OP THR PRESS. Sir, —“No More Super’s” letter in today’s issue prompts me to take a hand in the matter. “No Moi_e Super” is quite correct when he says engines run satisfactorily on standard grade petrol. The petrol engine is a heat engine, which converts the heat delivered to it from the petrol into useful mechanical work or horse-power. Now, a petrol is only as good as its calorific value; that is. its heat value, usually expressed in British thermal units. Oil companies will have the public to understand that all engines run better on tetra ethel lead loaded pet-

rol. I disagree with this. The cM* type of engine and quite a few XBOO’ ern ones, too, that are working®* 4.5 to 1 compression ratio or abouts, or, indeed, any engine tty * not inclined to knock or pink on saa* dard grades of petrol, cannot be ®* proved by tetra ethel lead compoßß® —Yours, etc., anti-knock. January 14, 1938. [When this letter was referred t» an official of the Vacuum Oil OW pany, he said that obviously ABB" Knock” was running an old car which was working on a lower®** pression ratio than its contempu*** models. The average compress*” ratio in 1927 was 4.55 to 1, end®" horse-power a cubic inch of dispacr ment was .256, In 1937. the ava*F horse-power a cubic inch of diS>®s* ment was about .45. To cope »*. this increase, petrol the various petrol companies, duced, at the wish of the car facturers, a petrol with a compre»*’j ratio of 6.14 to 1. This was achieve by using tetra ethyl lead, ana .j. petrol became a super fuel w . Tij knocking qualities for the use of the faster modem car, ana . though quite good for the running, an old car its advantages more fully by the high-powered ern car.]