Certain chemicals which are added to automotive gasolines to improve their performance, to reduce 'ping" or knock in high-compression, internal combustion engines. Tetraethyl lead is one well-known compound. The addition of small amounts of these chemicals has the effect of slowing down the explosion or burning of the air-gasoline vapor mixture in the combustion chamber, thus giving the piston a "push" instead of a sudden explosive blow. The compounds contribute also to smoother performance, of the engine and more mile; per gallon of fuel. antiknock compound any substance added to the fuel of an internal-combustion engine to prevent detonation of the fuel; specifically, tetraethyl lead. Antiknock compounds effectively raise the octane rating of a fuel so that the fuel burns properly in the combustion chamber of the engine.
