Why were alkyl lead compounds added?
The efficiency of a spark-ignited gasoline engine can be related to the compression ratio up to at least compression ratio 17:1 [15]. However any “knock” caused by the fuel will rapidly mechanically destroy an engine, and General Motors was having major problems trying to improve engines without inducing knock. The problem was to identify economic additives that could be added to gasoline or kerosine to prevent knock, as it was apparent that engine development was being hindered. The kerosine for home fuels soon became a secondary issue, as the magnitude of the automotive knock problem increased throughout the 1910s, and so more resources were poured into the quest for an effective “anti-knock”. A higher octane aviation gasoline was required urgently once the US entered WWI, and almost every possible chemical ( including melted butter ) was tested for anti-knock ability [16]. Originally, iodine was the best anti-knock available, but was not a practical gasoline additive, and was used a
