Coal oil is a liquid fuel produced by distilling coal, oil shale, or similar carbon-rich minerals. The term dates to the mid-1800s, when it described the kerosene-like fuel that replaced whale oil in lamps across North America. Today, “coal oil” is still used colloquially in parts of the United States and Canada as a synonym for kerosene, even though modern kerosene comes from petroleum rather than coal.
How Coal Oil Originated
In the 1840s and 1850s, the world ran on whale oil for lighting, and supplies were getting expensive. Abraham Gesner, a Canadian doctor and geologist, developed a process for distilling a clean-burning lamp fuel from coal and oil shale. He called the product “kerosene” and patented his method on March 27, 1855. The fuel was cheaper and more reliable than whale oil, and it spread rapidly. Within a decade, Gesner’s coal oil helped dismantle the commercial whaling industry and laid the groundwork for the modern petroleum industry.
The process worked by heating bituminous coal or oil shale in a sealed vessel, driving off vapors, and then cooling those vapors back into liquid. Different fractions condensed at different temperatures, and the lighter, cleaner-burning portion became the lamp oil sold as “coal oil.” Heavier residues were discarded or used for other purposes. Once crude petroleum was discovered in large quantities in Pennsylvania in 1859, refiners found they could produce the same type of kerosene more cheaply from petroleum. Coal-derived production faded, but the name “coal oil” stuck in everyday speech for generations.
Coal Oil vs. Kerosene
Functionally, coal oil and kerosene are the same product. Both are thin, flammable liquids that burn with a steady flame and relatively little smoke. The only real distinction is the source material: original coal oil came from distilling coal or oil shale, while kerosene today is refined from crude petroleum. The chemical composition is nearly identical, a mix of hydrocarbons in the range that vaporizes and burns cleanly in a wick-fed lamp or heater.
In rural parts of Appalachia, the Ozarks, and eastern Canada, older generations still call kerosene “coal oil.” You might hear someone refer to a “coal oil lamp” when they mean a standard kerosene lantern. The terms are interchangeable in everyday use.
What Coal Oil Was Used For
The primary use was always lighting. Before electricity reached rural homes, coal oil lamps were the standard way to light a room after dark. The fuel was poured into a glass reservoir, drawn up through a cotton wick, and lit. A glass chimney directed the flame and reduced flickering. Millions of these lamps were in use across North America and Europe from the 1850s through the early 1900s.
Beyond lighting, coal oil served as a household solvent and cleaning agent. People used it to remove tar, loosen rusted bolts, and clean grease from tools and machinery. It also found use as a folk remedy, though swallowing or applying kerosene to skin carries real health risks, including chemical burns to the mouth and throat, lung damage if inhaled into the airways, and poisoning. These folk uses have no medical support.
As a heating fuel, coal oil powered small portable stoves and space heaters, especially in areas without access to natural gas or firewood. Some early engines also ran on kerosene before gasoline became the dominant motor fuel.
Modern Coal-to-Liquid Technology
The idea of turning coal into liquid fuel never fully disappeared. In the 1920s, German chemists Franz Fischer and Hans Tropsch developed a process that converts coal into synthetic gasoline and diesel. The method works in two stages: first, coal is gasified at high temperatures to produce a mixture of carbon monoxide and hydrogen (called syngas). Then, that syngas passes over a catalyst, where the gases recombine into liquid hydrocarbons.
Germany used Fischer-Tropsch synthesis to fuel its military during World War II, when petroleum supplies were cut off. Decades later, South Africa built large-scale coal-to-liquids plants during the apartheid era, when international sanctions restricted oil imports. Those South African facilities still operate today, producing diesel, naphtha, and chemical feedstocks from coal.
The process can be tuned to favor different products. Lower temperatures and specific catalysts push the reaction toward heavier waxes, which are then cracked into diesel. Higher temperatures produce lighter fuels and chemical building blocks. The final output is fractionated into diesel, naphtha, and lighter gases, much like a conventional petroleum refinery. Coal-to-liquids technology remains expensive compared to simply refining crude oil, so it tends to be viable only where petroleum is scarce or strategically unreliable.
Why the Term Persists
Language often outlasts the technology that created it. “Coal oil” survives for the same reason people say “dial” a phone number or “roll down” a car window. The original coal-derived product was so widespread in the 1800s that the name became embedded in regional dialects. In areas where kerosene lamps remained common well into the 20th century, the old term simply never got replaced. If you encounter “coal oil” in conversation, on a product label, or in old literature, it almost always means kerosene.