Ethyl Anti-Knock Gas
G.M. scientists discover the anti-knock properties of tetraethyl lead gasoline.
General Motors scientists in 1921 discovered the anti-knock properties of tetraethyl lead as an additive to gasoline. By 1923, many American motorists would be driving into service stations and saying, “Fill ‘er up with Ethyl.”
Early internal combustion engines often suffered from a severe “knocking,” 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.
Automobiles powered with gasoline had been the least popular models at the November 1900 first U.S. auto Show in New York City’s Madison Square Garden.
General Motors chemists Thomas Midgely Jr. and Charles F. Kettering tested many gasoline additives, including arsenic.
On December 9, 1921, 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.
Early experiments at GM examined the properties of knock suppressors such as bromine, iodine and tin — comparing these to new additives such as arsenic, sulfur, silicon and lead.
The world’s first anti-knock gasoline containing a tetra-ethyl lead compound went on sale at the Refiners Oil Company service station in Dayton, Ohio. A bolt on “Ethylizer” can be seem running vertically alongside the visible reservoir. Photo courtesy Kettering/GMI Alumni Foundation.
When the two chemists synthesized tetraethyl lead and tried it in their one-cylinder laboratory engine, the knocking abruptly disappeared. Fuel economy also improved. “Ethyl” vastly improved gasoline performance.
“Ethylizers” debut in Dayton
Although being diluted to a ratio of one part per thousand, the lead additive yielded gasoline without the loud, power-robbing knock. With other automotive scientists watching, the first car tank filled with leaded gas took place on February 2, 1923, at the Refiners Oil Company service station in Dayton, Ohio.
In the beginning, GM provided Refiners Oil Company and other service stations special equipment, simple bolt on adapters called “Ethylizers” to meter the proper proportion of the new additive.
“By the middle of this summer you will be able to purchase at approximately 30,000 filling stations in various parts of the country, a fluid that will double the efficiency of your automobile, eliminate the troublesome motor knock, and give you 100 percent greater mileage,” Popular Science Monthly reported in 1924.
By the late 1970s, public health concerns resulted in the phase-out of tetraethyl lead in gasoline, except for aviation fuel.
Anti-knock gasoline containing a tetraethyl lead compound also proved vital for aviation engines during World War II, even as danger from the lead content increasingly became apparent.
Powering Victory in World War II
Aviation fuel technology was still in its infancy in the 1930s. The properties of tetraethyl lead proved vital to the Allies during World War II. Advances in aviation fuel increased power and efficiency, resulting in the production of 100-octane aviation gasoline shortly before the war.
Phillips Petroleum – later ConocoPhillips – was involved early in aviation fuel research and had already provided high gravity gasoline for some of the first mail-carrying airplanes after World War I.
Phillips Petroleum produced tetraethyl leaded aviation fuels from high-quality oil found in Osage County, Oklahoma, oilfields.
Phillips Petroleum produced aviation fuels before it produced automotive fuels. The company’s gasoline came from the high-quality oil produced from Oklahoma’s Seminole oilfields and the 1917 Osage County oil boom.
Although the additive’s danger to public health was underestimated for decades, tetraethyl lead has remained an ingredient of 100 octane “avgas” for piston-engine aircraft.
Tetraethyl lead’s Deadly Side
Leaded gasoline was extremely dangerous from the beginning, according Deborah Blum, a Pulitzer-Prize winning science writer. “GM and Standard Oil had formed a joint company to manufacture leaded gasoline, the Ethyl Gasoline Corporation,” she noted in a January 2013 article. Research focused solely on improving the formula, not on the danger of the lead additive.
A 1932 magazine advertisement promoted the Ethyl Gasoline Corporation fuel additive as a way to improve high-compression engine performance.
“The companies disliked and frankly avoided the lead issue,” Blum wrote in “Looney Gas and Lead Poisoning: A Short, Sad History” at Wire.com. “They’d deliberately left the word out of their new company name to avoid its negative image.”
In 1924, dozens were sickened and five employees of the Standard Oil Refinery in Bayway, New Jersey, died after they handled the new gasoline additive.
By May 1925, the U.S. Surgeon General called a national tetraethyl lead conference, Blum reported, and an investigative task force was formed. Researchers concluded there was ”no reason to prohibit the sale of leaded gasoline” as long as workers were well protected during the manufacturing process.
So great was the additive’s potential to improve engine performance, the author notes, by 1926 the federal government approved continued production and sale of leaded gasoline. “It was some fifty years later – in 1986 – that the United States formally banned lead as a gasoline additive,” Blum added.
By the early 1950s, American geochemist Clair Patterson discovered the toxicity of tetraethyl lead; phase-out of its use in gasoline began in 1976 and was completed by 1986. In 1996, EPA Administrator Carol Browner declared, “The elimination of lead from gasoline is one of the great environmental achievements of all time.”
Learn more about high-octane aviation fuel in Flight of the Woolaroc.
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Recommended Reading: An Illustrated Guide to Gas Pumps
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Citation Information – Article Title: “Ethyl Anti-Knock Gas.” Authors: B.A. Wells and K.L. Wells. Website Name: American Oil & Gas Historical Society. URL: https://aoghs.org/products/tetraethyl-lead-gasoline. Last Updated: December 3, 2024. Original Published Date: December 7, 2014.
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