Gasoline and gasoline additives

DEFINITION: Liquid fuel produced from petroleum, and chemicals that may be added to such fuel to change the way it performs, cleans, lubricates, or appears

Gasoline plays a significant role in the transportation industry throughout the world, and gasoline additives play an important role in increasing both the octane and performance of gasoline-fueled vehicles. The burning of gasoline, however, has many negative impacts on the environment and on human health.

Gasoline is a liquid fuel that contains a mixture of liquid hydrocarbons. Refined from crude oil, gasoline is shipped to storage terminals from refineries in pipelines that are also used to transport other liquid products. It is then trucked from the storage terminals to retail outlets.

Gasoline varies widely in its composition owing to refineries’ mixing of crude oil from various locations, the mixing that may occur between gasoline and other products shipped in shared pipelines, and the various additives mixed in by individual companies. The invention of the automobile in the late nineteenth century transformed gasoline from a useless by-product of oil refining to a valuable transportation fuel. By the 1920s, automobiles, gasoline, and gasoline stations were major elements of everyday life in the United States. Gasoline companies began putting additives in gasoline for marketing purposes, to distinguish their products from those of competitors.

Among the many different types of gasoline additives are hybrid compound blends, alcohols that act as oxygenators, ethers, antioxidants, and antiknock agents. Many gasoline additives produce emissions that are harmful to the environment and can cause health problems; others are beneficial to the environment in that they reduce air pollution. The first gasoline additive used was tetraethyl lead, which increased the octane of the gasoline and also acted as a lubricant. Benzene and toluene have been commonly used as additives. Methyl tertiary-butyl ether (MTBE) is an additive that increases octane and reduces the emission of pollutants by increasing the amount of oxygen in gasoline. However, MTBE is no longer used because of environmental and health concerns.

Gasoline and the Environment

When gasoline is burned, it releases a number of harmful pollutants into the air, including carbon monoxide, nitrogen oxide, particulate matter, and carbon dioxide, a major greenhouse gas that has been linked to global warming. In addition, the leakage of gasoline from storage tanks and from pipelines has the potential to contaminate water supplies.

Both gasoline and its additives can pose health hazards when burned or vaporized. Exposure to lead, which was, until the 1970s, the additive of choice, is known to cause cancer and other serious health problems. Benzene vapor from gasoline can cause headaches and dizziness, and high levels can cause rapid heart rate and tremors; benzene is also a carcinogen. Exposure to toluene can cause headaches, respiratory irritation, and nausea.

MTBE, which replaced lead as an octane enhancer in 1979, is an oxygenate that was believed to have positive effects on the environment. It reduces the amount of toxic emissions as it causes more of the gasoline to burn. Inhalation of MTBE was not believed to pose a hazard to health; however, some concerns began to be expressed in the late twentieth century regarding the additive’s potential to contaminate drinking water. As research began to confirm these concerns, alternative additives began to be explored. MTBE was phased out of use beginning in 2006.

Environmental Regulations

As early as 1924, exposure to lead was determined to be a serious health hazard. Nevertheless, the levels of lead in gasoline increased through the 1950s as motorists wanted larger, faster cars, and increasing the amount of lead in gasoline increased both octane and engine performance. As a result of further research and greater awareness of the damage to both the environment and human health caused by the use of leaded gasoline, the 1970 amendments to the Clean Air Act set air-quality standards and included a plan for eliminating lead in gasoline. This legislation also set limits of acceptability for the amount of carbon monoxide, hydrocarbons, and nitrogen oxides in vehicle emissions. In 1976, all new vehicles were required to be equipped with catalytic converters to reduce pollutants in emissions. Only unleaded gas, which had been introduced in 1975, could be used in vehicles with catalytic converters. The manufacture of these cars did much to phase out the use of lead in gasoline. On January 1, 1996, the use of leaded gasoline in on-road vehicles was banned in the United States.

Many other laws have been enacted that include provisions aimed at making gasoline less harmful to the environment and less of a health hazard. The 1990 amendments to the Clean Air Act set a target date of 1995 for all gasoline sold in certain metropolitan areas to be reformulated so that it would burn cleaner. This measure was taken to reduce ground-level ozone, a serious problem in many large cities, such as Dallas, Chicago, and New York. In 1990, the US Environmental Protection Agency (EPA) also required the replacement of all buried single-lined gasoline storage tanks with double-lined tanks to decrease the possibility of leakage. In 2006, the reduction of sulfur levels in gasoline became a priority. Refineries were required to reduce sulfur levels in gasoline, and new vehicles were mandated to have pollution-control devices that require low sulfur content to operate properly.

The negative effects of gasoline and its additives on the environment and health remained major concerns worldwide in the early twenty-first century. However, lead gasoline was banned in Europe in 2000, and in 2009, the European Union passed legislation requiring gasoline stations to install systems for capturing and recycling toxic emissions. Leaded gasoline was still used in Asia, Africa, and some Latin American countries until it was banned worldwide in 2021 (other than limited use in small aircraft).

In the twenty-first century, most gasoline additives are detergents, which help lubricate and clean the engine and reduce corrosion. Other additives raise the gasoline’s octane rating, which is a measure of the gasoline’s ability to withstand the compression that occurs within the engine. About 98 percent of all gas in the United States is mixed with ethanol, a biomass additive that reduces pollution. Other blends are also available, including E15 and E85. E15, also called unleaded 88, contains between 10.5 and 15 percent ethanol; E85 contains up to 85 percent ethanol and is for use in flexible-fuel vehicles.

Bibliography

Daud, Sarbani, et al. “A Review of Fuel Additives’ Effects and Predictions on Internal Combustion Engine Performance and Emissions.” AIMS Energy, vol. 10, no. 1, 2022, pp. 1–22, doi:10.3934/energy.2022001. Accessed 26 Oct. 2025.

Dinan, Terry, and David Austin. Reducing Gasoline Consumption: Three Policy Options. Novinka Books, 2003.

"Ethanol Fuel Basics." U.S. Department of Energy, afdc.energy.gov/fuels/ethanol-fuel-basics. Accessed 26 Oct. 2025.

"Registered Gasoline Additives." US Environmental Protection Agency, 28 Apr. 2025, www.epa.gov/gasoline-standards/registered-gasoline-additives. Accessed 26 Oct. 2025.

Reynolds, John G., and M. Rashid Khan. Designing Transportation Fuels for a Cleaner Environment. Taylor & Francis, 1999.

Stolark, Jessie. "A Brief History of Octane in Gasoline: From Lead to Ethanol." Environmental and Energy Study Institute, 30 Mar. 2016, www.eesi.org/papers/view/fact-sheet-a-brief-history-of-octane. Accessed 26 Oct. 2025.

United Nations Environment Programme. Phasing Lead Out of Gasoline: An Examination of Policy Approaches in Different Countries. United Nations Publications, 2000.