Octane requirement increase , gasoline engine

In some circumstances, the octane number of the gasoline used in the engine must be increased to prevent knock caused by accumulated deposits. This phenomenon is called Octane Requirement Increase (ORI). Both prevention and reversal of ORI are difficult to achieve. 

It may therefore be concluded that if further restrictions on gasoline lead content are considered desirable for environmental reasons, their introduction should be phased in with the introduction of engines designed to minimise the inevitable increase in total energy consumption by having octane requirements in line with the optimum RON described in this report. 

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