An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which ignition occurs.
The mixture known as gasoline, when used in high compression internal combustion engines, has a tendency to ignite early before the correctly timed spark occurs (pre-ignition or detonation) causing a damaging "engine knocking" (also called "pinging" or "pinking") noise. Early research into this effect was led by A.H. Gibson and Harry Ricardo in England and Thomas Midgley, Jr. and Thomas Boyd in the United States. The discovery that lead additives modified this behavior led to the widespread adoption of the practice in the 1920s and therefore more powerful higher compression engines. The most popular additive was tetraethyllead. However, with the discovery of the environmental and health damage caused by the lead, and the incompatibility of lead with catalytic converters found on virtually all US automobiles since 1975, this practice began to wane in the 1980s. Most countries are phasing out leaded fuel although different additives still contain lead compounds. Other additives include aromatic hydrocarbons, ethers and alcohol (usually ethanol or methanol).
'The typical antiknock agents in use are:
- Tetraethyllead (Still in use as a high octane addative)
- Methylcyclopentadienyl manganese tricarbonyl (MMT)
- Ferrocene
- Iron pentacarbonyl
- Toluene
- Isooctane
Read more about Antiknock Agent: Tetraethyllead, MMT, Ferrocene, Iron Pentacarbonyl, Toluene, 2,2,4-Trimethylpentane (isooctane)
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