|Kind of petrol
In Summer time, petrol producers should fight steam bubble formation by adding more hard boiling portions, containing slightly more energy. In winter time the cold start of the engine is made
easier by adding more light-boiling components, thus less non-boiling portions end up in the engine oil. Petrol should boil early, gasify easily, and, nevertheless, be ignition-reluctant.
Petrol consists mainly of aliphatic hydrocarbons. They evolve during the distillation of crude oil. In this process, the different substances are separated according to their boiling points. To raise their
portion of approx. 30%, special processes as for example the cracking (chopping up of big molecule chains) are common. The high antiknock characteristic typical for petrol comes about from
interlinking the molecule chains (polymerization).
Other important characteristics like for example the avoidance of carbonization in intake valves are accomplished by additives. The high antiknock characteristics and the resulting ignition-
reluctance of the petrol are due to the working principle of the petrol engine. While compressing the fuel in the combustion chamber it must not inflame itself. The spark plug should ignite the fuel
mixture at the ignition time, precisely calculated by the control device. The higher the compression, the more efficient the combustion, and the more performance the petrol engine may produce. The
flash point is the temperature at which inflammable vapors evolve. For petrol it is -20°C, the burning point is 240°C. Thus, petrol belongs to danger class AI. (flash point below 21°C).
Petrol vapors are invisible, heavier than air and highly explosive.