FACTS ABOUT PETROL

Dominion, Volume 27, Issue 35, 4 November 1933, Page 22

FACTS ABOUT PETROL

First and Second Grade USE FOR DIFFERENT WORK There are few corners of the earth where petroleum in some form is not known or used. Yet, in spite of the commonness of its uses it still remains one of nature’s most complicated chemical sciences. The elementary chemistry of petroleum, however, is quite simple; it is composed of but two elements—hydrogen nad carbon. Traces of other compounds containing sulphur, nitrogen and oxygen are but these are negligible in amount as compared to the hydrocarbons. The relation of the carbon and hydrogen atoms in combination determine the characteristics of a motor fuel. The highly complicated combination of these elements in combination would be of little interest to the average motorist, but what is of interest to the motorist is their reaction to combustion under service conditions. When a perfect combustion takes place in the cylinder of a motor the hydrogen in a motor fugl turns to water and the carbon to heat. When the combustion is incomplete the carbon element turns to material carbon and is deposited within the cylinder—thus the sooty substance in a cylinder and on the spark-plug when a cylinder is missing. It is readily apparent that heat, then, is the generated energy or power of an internal combustion en.gine. The amount of heat or power generated by a motor unit is largely dependable upon the fuel used. The heat units, or calorific value, of a motor fuel, measured in British thermal units, vary in direct ratio with the gravity of the fuel, the lower gravity fuels having a greater calorific value per gallon consumed; that is, the amount of heat given off in the combustion of a gallon of heavy fuel is greater than that supplied by a fuel of higher gravity. In America and many other countries of the world the average motor fuels used are much heavier than those used in New Zealand, and American cars and trucks are designed to use the heavier fuels. The common term “second grade” applied to petrol in New Zealand is stated to be a misnomer as the lowest grade on the market here has better specifications than the ordinary American first grade, while the first grade motor spirit marketed in New Zealand is comparable to the American domestic aviation ngtrql. Investigations and tests indicate that the higher gravity fuels are eminently suited for English motor-cars and for city motoring where frequent starting and stopping is involved and the motor seldom becomes properly heated. For commercial and heavy work, however, and for most American cars, the lower gravity fuels are recommended as their higher calorific value means greater power and more miles per - gallon which makes them, without doubt, a more economical proposition.