Octane: A saturated hydrocarbon (alkane) with the chemical formula C8H18. The word is formed from octo- (eight, as in eight carbon atoms) and –ane (a suffix denoting a hydrocarbon).
Used with a prefixed numeral or adjective (e.g., “high-octane”), octane is a truncation of octane number, “a number indicating the anti-knock properties of a motor or aviation fuel.” (Oxford English Dictionary). Octane number is often expressed as octane rating, a measure of “a fuel’s tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner” (Wikipedia). An octane rating of 90 originally represented a fuel blend containing 90 percent iso-octane; other substances with similar anti-knock properties may be substituted for iso-octane.

Chevron station, Oakland, Feb. 27, 2011
Since at least about 1989, octane has also been used metaphorically to signify power, vigor, excitement, or “oomph,” as in this rather odd example: “People were suffused with the Judeo-Christian octane of individual destiny...” (“A Plunge into the Present,” by Ron Suskind, New York Times Magazine, Dec. 2, 2001.)
With rising gasoline prices in the news again, I’ve been thinking about octane, a word I’d been aware of since childhood but had never really understood. When I thought of it at all, I imagined octane as a magical additive (like Techron, perhaps), that was mixed into gasoline to make it more powerful. I may have associated it with knocking—the explosive sound made by inefficient combustion in a car engine—but I’d never really contended with knocking, so I couldn’t say for sure.
As it happens, I’ve been reading Deborah Blum’s fascinating The Poisoner’s Handbook: Murder and the Birth of Forensic Medicine in Jazz Age New York. In her chapter on mercury poisoning, Blum includes a digression on tetraethyl lead (TEL), the original antiknock compound. Two General Motors employees, Thomas Midgley Jr., and Charles Kettering, discovered in 1921 that TEL “smoothed out the rough patches in gasoline combustion.” That was good news for drivers but very bad news for workers in Standard Oil’s TEL processing plant, nicknamed “the looney gas building.”
The men who worked there, in the clanking heat and drifting vapors, had become a little odd—moody, short-tempered, unable to sleep. They’d started getting lost on the familiar plant grounds, sometimes had trouble remembering their friends. And then in September 1924 the workers started collapsing, going into convulsions, babbling deliriously. By the end of October, thirty-two of the forty-nine TEL workers were in the hospital, and five had died.
Standard Oil’s response was to claim that the men “probably went insane because they worked too hard.” In subsequent years, most of the research into lead poisoning was funded by the lead industry. It wasn’t until the 1940s and 1950s, when TEL was first associated with environmental pollution, that pressure to remove TEL from gasoline began to mount. And it wasn’t until 1972 that the newly created US Environmental Protection Agency ordered a phasing out of leaded gasoline. The phaseout was completed in 1986, but TEL continued to be used outside the United States for many years. In the United States and elsewhere, various substitutes, including ethanol and synthetic iso-octane, are used as antiknock agents. (This post-Jazz Age history comes from a Wikipedia entry.)
“Octane” turns up occasionally in a metaphorical sense—signifying “energy” rather than “efficiency”—in brand names such as Octane Fitness, a manufacturer of elliptical machines for home or gym use; Octane, a British magazine covering “the world’s greatest classic & performance cars”; and Octane (tagline: “Fuel the Hunt”), a maker of archery paraphernalia.
Octane is also the name of a hard-rock band and the title of a 2003 movie about a woman who “must save her rebellious teenage daughter who runs off with a bizarre group of blood-letting psychos.”
UPDATE: The US gas-station chain 76 (formerly Union 76) takes its name from 76 gasoline, introduced by Union Oil in 1932. The numeral refers both to the American “Spirit of 76” and to the gasoline’s octane rating in 1932. Phillips 66, owned by the same parent company (ConocoPhillips) as 76, was named for Highway 66, on which the fuel was originally tested in 1927, and for the speed at which the test car was driving: 66 miles per hour.