Bearcat Ethyl Motor Fuel Mug

In early internal combustion engines, “knocking” resulted from the out-of-sequence detonation of the gasoline-air mixture in a cylinder. The constant shock added to exhaust valve wear and frequently damaged engines. After five years of lab work to find an additive to eliminate pre-ignition “knock” problems of gasoline, General Motors researchers Thomas Midgely Jr. and Charles Kettering discovered the anti-knock properties of tetraethyl lead. Their early experiments had examined the properties of knock suppressors such as bromine, iodine and tin – and compare these to new additives such as arsenic, sulfur, silicon and lead.