be sere o jv Why Shell has been RE-FORMED gr°1]F 5 6 IN LONG CHAINS ORDINARY PETROL MOLECULES burn loo quickly In the old days the thing was to get a petrol which would burn or explode as quickly as possible. This was all right until engineers found that the way to get more power from a given engine was to increase its compression ratio. They then found that this in creased cylinder pressure caused ordinary petrol to explode too quickly This detonation or pinking resulted in loss of power and an over-heated engine. The problem, then, was to produce a petrol which had a rate of burning suited to the modern engine. SHELL has solved the problem by changing its molecular structure This is done by a process called re-forming Re-forming takes the atoms of carbon and hydrogen, which are present in all motor spirit, and puts them together in compact groupings instead of in long chains as they are in ordinary petrol In this condensed formation they combine regularly and evenly instead of spasmodically with the oxygen supplied by the air from the carburettor: thus combustion is controlled and pinking prevented In this way SHELL offers you the advantages of a pure petrol in a form suited to the modern engine -t£e<£ SH EU r"E molecules into compact Advertisement Designer H. Schleger. Agent: Regent Advertising Service Ltd. Advertiser Shell-Mex B.P. Ltd.

Modern Publicity en | 1938 | | page 58