Unleaded Gas 101: Understanding the Basics of Unleaded Fuel

The health and environmental risks of lead exposure are so well known today, it may be difficult to imagine it was ever a key ingredient in gasoline. But for about 70 years, refineries added tetraethyl lead to gasoline to improve engine performance.

In 1973, the EPA issued its first limitations on lead in gasoline, and auto manufacturers began to build cars that would run on unleaded gas. By the mid 1980s, unleaded gasoline was the standard fuel for passenger cars, and in 1996 the Clean Air Act finally banned the sale of all leaded gas in the U.S.^[1] 

Today, you’ll find only diesel and unleaded gasoline – available in three different octane ratings – for sale at American gas stations. Here’s what you need to know about unleaded gasoline.

What is unleaded gas and how does it work?

Unleaded gas refers to gasoline processed without the inclusion of tetraethyl lead. Most vehicles that use gasoline employ a spark-ignited combustion engine.^[2] Fuel enters the combustion chamber, creates a fuel mixture with air, and is then ignited by the spark plug. The combustion gas expands to push the piston, rotate the crankshaft, and move the gears — which move the vehicle.^[3]

As the vehicle moves, the exhaust expels the remaining combustion gas. Leaded gasoline burned through the engine can contaminate the environment and impact people with lead exposure.

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What are the pros and cons of unleaded gas?

Lead gasoline was created in 1921 and became the standard fuel for vehicles before decades of research established how lead gasoline could harm the environment and public. The U.S. Energy Information Administration notes that any gasoline burned, including unleaded, contributes to air pollution and produces carbon dioxide. 

The current use of unleaded gas includes pros and cons that impact vehicle performance and the environment.

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Unleaded vs. premium gas: What’s the difference?

With the exception of diesel fuel, all gasoline sold at gas stations is some form of unleaded gas. The different unleaded fuel options you see at a gas station include regular, midgrade, and premium gas, all of which have different octane levels.

Octane levels explained

The octane rating of different fuel types measures fuel stability, and fuel grades with higher octane ratings have greater fuel stability. Both spontaneous and controlled explosions occur in an engine. However, spontaneous combustion creates pressure that can disrupt and damage engines. Octane ratings measure the fuel’s ability to resist or reduce this spontaneous combustion damage, which is often referred to as “engine knocking.” Although newer-model cars have features to prevent engine knocking, higher octane fuel may also improve engine performance, fuel efficiency, and reduce CO2 emissions.

When selecting fuel options at a gas station, you’ll generally see three separate numbers between 87 and 94 listed on the pumps. This number refers to the octane rating of the gasoline. All three of these options are unleaded gasoline, though each falls into one of the following specific categories:

• Regular: The lowest octane fuel that’s generally labeled as 87

• Midgrade: The middle range of octane fuel that’s generally labeled as 89 or 90

• Premium: The highest range of octane fuel that’s generally labeled between 91 and 94

You may also see a pump labeled with the number 88, so you should know how unleaded 88 differs from unleaded 87 and 89. Unleaded 88 simply contains more ethanol than unleaded 87 gasoline. Unleaded 87 typically has 10% ethanol, while unleaded 88 has 15% ethanol. Unleaded 88 can be used in many modern vehicles, but it shouldn’t be used elsewhere.

Which gas should you choose for your engine?

All vehicle manufacturers either recommend or require the use of an unleaded gasoline with a specific octane level. Most manufacturers list this information in the owner’s manual. Many vehicle engines are designed to run on regular gasoline, but some manufacturers recommend midgrade or premium gasoline. Choosing the correct gas for your vehicle helps your engine run optimally.

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How much does unleaded gas cost?

The average price of regular unleaded gasoline in the U.S. for dollars per gallon was $3.42 on Jan. 23, 2023; $3.49 on Jan. 30; and $3.44 on Feb. 6, according to the U.S. Energy Information Administration’s Gasoline and Diesel Fuel Update.^[6] This data displays an increase from the previous year and fluctuates from week to week. In most regions of the United States — with the exception of the West Coast — a similar pattern emerged week over week and year over year. 

Here are the average costs of unleaded gasoline during the first week of February 2023 by region:

• East Coast: $3.41

• Midwest: $3.30

• Gulf Coast: $3.09

• Rocky Mountain: $3.69

• West Coast: $4.12

A number of factors affect gasoline prices, including:^[7] 

• Crude oil costs: Crude oil costs impact fuel prices the most. The factors that influence crude oil prices include the OPEC and non-OPEC supplies, the OECD and non-OECD demand, financial markets, spot prices, and the balance between supply and demand.

• Refining costs and profits: These factors vary by season and by region, as different refineries use different types of crude oil and processing technology to produce gasoline that meets the reduced air pollution requirements in different areas of the country.

• Distribution and marketing costs and profits: Local fuel stations may adjust prices based on their individual marketing strategies. Distribution to each retail outlet also affects prices, as some gas station businesses own refineries while others are independent businesses who need to purchase gasoline for resale.

• Taxes: Various taxes also influence the price at the pump, including federal, excise, state, sales, and local taxes.

Who influences crude oil costs?

The Organization of the Petroleum Exporting Countries (OPEC) is an intergovernmental alliance between 13 countries that produce around 40% of global crude oil and are responsible for about 60% of global petroleum trade through their exports. The group has expanded since its 1960 founding by Iraq, Iran, Kuwait, Saudi Arabia, and Venezuela. Non-OPEC supplies come from all countries not involved with the OPEC, including the U.S., China, and India. 

Made up of various countries in North America, Europe, South America, and the Asia-Pacific, the Organization of Economic Cooperation and Development (OECD) discusses and collaborates on certain global issues. In 2010, these countries consumed 53% of the world’s crude oil — despite producing less than non-OECD countries.

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Unleaded gas FAQs

Knowing which unleaded gasoline to use can help prevent engine damage, and using the wrong gasoline could increase the likelihood of long-term damage or decreased efficiency. Here are answers to some commonly asked questions about unleaded gas.