Salient: Victoria University Students' Paper. Vol. 28, No. 11. 1965.
The wrong degree of volatility can also cause another irritating complaint known as "carburettor icing." When petrol evaporates, it takes its latent heat of vaporisation from the surrounding air. Under certain conditions of temperature and humidity, such as those found in certain South Island areas for up to six months of the year, moisture condenses out of the air, and forms ice on carburettor surfaces.
A thickening film of ice in the carburettor can immobilise a car somewhat better than a vapour lock, because when the ice goes, the water that forms it remains to contaminate the fuel. The risk of carburettor icing can be reduced by lessening the volatility of the fuel, but it is generally much more effective to use anti-icing compounds, such as "surface active ingredients." which prevent ice forming on surfaces.
The volatility range of a gasoline must be carefully chosen, and tailored to meet the prevailing elimatic conditions.
In certain continental areas such as the United States, gasoline varies from region to region. The product you fill your tank with in Los Angeles will probably be quite different from that you buy in Dallas. Similarly, a gasoline ideal for New Zealand would be worse than useless in Aden.