Gasoline basics

Gasoline is a petroleum product

Gasoline is a fuel made from crude oil and other petroleum liquids. Gasoline is mainly used in vehicle engines. Petroleum refineries and blending facilities produce finished motor gasoline for retail sale at gasoline fueling stations.

Most of the gasoline that petroleum refineries produce is actually unfinished gasoline (or gasoline blendstocks). Gasoline blendstocks, finished gasoline, and fuel ethanol are blended to make finished motor gasoline in different grades and formulas at blending terminals. Some companies also blend detergents and other additives with their gasoline before delivering to their retail outlets. Blending terminals are more numerous and widely dispersed than petroleum refineries, and they have equipment for filling tanker trucks that transport finished motor gasoline to retail outlets.

Most of the finished motor gasoline sold in the United States contains about 10% fuel ethanol by volume. Ethanol is added to gasoline mainly to meet the requirements of the Renewable Fuel Standard, which is intended to reduce greenhouse gas emissions and the amount of oil the United States imports from other countries.

Gasoline varies by grade

Three main grades of gasoline are sold at retail gasoline refueling stations:

• Regular
• Midgrade
• Premium

Some companies have different names for these grades of gasoline, such as regular, unleaded, mid-grade, medium, super, premium, or super premium, which all indicate the octane rating—the antiknock property of gasoline. (No grade of motor gasoline now sold in the U.S. contains lead.) The lowest octane rating gasoline is usually the least expensive. Vehicle manufacturers recommend the grade of gasoline each model of their vehicles should use.

Gasoline also varies by formulation

In addition to the grade of motor gasoline, the formulation of gasoline may differ, depending on the location where it is sold and the season of the year. Federal and state air pollution control programs that aim to reduce carbon monoxide, smog, and air toxins require oxygenated, reformulated, and low-volatility gasoline. Some areas of the country are required to use specially formulated gasoline to reduce certain emissions, and the formulation may change during winter and summer months. These area-specific requirements mean that gasoline is not the same everywhere.

Gasoline produced for sale in one area of the United States might not be authorized for sale in another area. The characteristics of gasoline depend on the type of crude oil used to produce it and the setup of the refinery that produces it. Gasoline characteristics are also affected by other ingredients that may be included in the blend, such as ethanol.

Uses of gasoline

Gasoline is the primary U.S. transportation fuel

In 2022, Americans used about 3,215,613,000 barrels (or about 135 billion gallons) of finished motor gasoline and about 4,419,000 barrels (or about 0.19 billion gallons) of finished aviation gasoline. Motor gasoline is one of the most consumed fuels in the United States and the main product that U.S. oil refineries produce. Most of the finished motor gasoline sold for vehicles in the United States is about 10% fuel ethanol by volume.

U.S. consumers use gasoline in:

• Cars, sport utility vehicles, light trucks, and motorcycles
• Recreational vehicles and boats
• Small aircraft
• Equipment and tools used in construction, farming, forestry, and landscaping
• Electricity generators for portable and emergency power supply

In 2022, total gasoline consumption, based on energy content (in British thermal units), accounted for about 57% of total transportation energy consumption, and based on volume (in barrels), 45% of total petroleum consumption.¹

Light-duty vehicles (cars, sport utility vehicles, and small trucks) account for about 91% of all gasoline consumption in the United States.²

History of gasoline

Gasoline was initially discarded

Edwin Drake dug the first U.S. oil well in Pennsylvania in 1859 and distilled the oil to produce kerosene for lighting. Although other petroleum products, including gasoline, were also produced in the distillation process, Drake had no use for them, so he discarded them. It wasn't until 1892, when the automobile was invented, that gasoline was recognized as a valuable fuel. By 1920, 9 million vehicles powered by gasoline were on the road, and service stations selling gasoline were opening around the country. Today, gasoline is the fuel for nearly all light-duty vehicles in the United States.

Gasoline octane and lead levels increased over time

By the 1950s, cars were becoming bigger and faster. Gasoline octane increased, and lead was added to improve engine performance.

Leaded gasoline was eventually taken off the U.S. market

Unleaded gasoline was introduced in the 1970s, when health problems from lead became apparent. In the United States, leaded gasoline for use in on-road vehicles was completely phased out as of January 1, 1996. Most other countries have also stopped using leaded gasoline in vehicles. In the United States, retail gasoline is usually sold in three grades based on octane levels: regular, midgrade, and premium.

Ethanol is added to gasoline

In 2005, the U.S. Congress enacted a Renewable Fuel Standard (RFS) that set minimum requirements for using renewable fuels, including ethanol in motor fuels. In 2007, the RFS targets were set to rise steadily to 36 billion gallons by 2022. In 2022, about 13.6 billion gallons of ethanol were added to gasoline in the United States. In most areas of the country, retail finished motor gasoline is about 10% ethanol by volume.

Gasoline and the environment

Gasoline use contributes to air pollution

Gasoline is a toxic and highly flammable liquid. The vapors gasoline gives off when it evaporates and the substances it produces when it is burned (carbon monoxide, nitrogen oxides, particulate matter, and unburned hydrocarbons) contribute to air pollution. Burning gasoline also produces carbon dioxide, a greenhouse gas.

Laws like the Clean Air Act reduce environmental effects

Most consumers use gasoline in cars, light trucks, and motorcycles, but they also use it in small aircraft, boats and other watercraft, and landscaping and construction equipment. Some U.S. environmental laws focus on reducing pollution from these sources.

The Clean Air Act (the Act) seeks to reduce air pollution in the United States. Specifically, the Act (first passed in 1970) and its amendments require engines and fuels to produce less air pollution—among other requirements.¹ To meet the goals set to reduce air pollution, the U.S. Environmental Protection Agency (EPA) took several actions to reduce pollution from gasoline use:

• Required emissions-control devices and cleaner burning engines
  Emissions-control devices on passenger vehicles were required beginning in 1976. In the 1990s, the EPA established emissions standards for other types of vehicles and for engines in gasoline-burning, non-road equipment.²
• Removed leaded gasoline for use in vehicles
  Lead in gasoline proved to be a public health concern. The move away from leaded gasoline began in 1976, when catalytic converters were installed in new vehicles to reduce the emissions of toxic air pollutants. Vehicles equipped with a catalytic converter cannot operate on leaded gasoline because the presence of lead in the fuel damages the catalytic converter. Leaded gasoline for vehicles was completely phased out of the U.S. fuel system by 1996. Leaded aviation gasoline is allowed in piston-engine aircraft. The U.S. government is supporting research on alternative, lead-free fuels for those types of aircraft.³
• Required reformulated gasoline
  Beginning in 1995, the Clean Air Act Amendments of 1990 required cleaner-burning reformulated gasoline to reduce air pollution in metropolitan areas that had significant ground-level ozone pollution.⁴
• Required ultra-low sulfur gasoline
  As of January 1, 2017, refiners are required to supply gasoline with 97% less sulfur content than the gasoline made in 2004. Gasoline with lower sulfur content reduces emissions from old and new vehicles and is necessary for advanced vehicle emission-control devices to work properly.⁵
• Reduced gasoline leaks
  Gasoline leaks happen at gas stations every day. As people fill up their gas tanks, gasoline drips from the nozzle onto the ground and vapors leak from the open gas tanks into the air. Gasoline leaks can also happen in pipelines or in underground storage tanks where they can't be seen. Beginning in 1990, all underground storage tanks had to be replaced by tanks with double lining. The double lining provides an additional safeguard for preventing leaks.⁶

Methyl tertiary butyl ether (MTBE), one of the chemicals added to gasoline to help it burn cleaner, is toxic, and a number of states started banning MTBE in gasoline in the late 1990s. By 2007, the U.S. refining industry voluntarily stopped using MTBE in reformulated gasoline for sale in the United States. MTBE was replaced with ethanol, which is not toxic.⁷