Reader Q&A: What's up with Arizona's special gasoline blends and are they worth the cost?

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This is part of a monthly series answering readers' climate-related questions and highlighting Arizona's unsung climate leaders. The stories aim to help connect and inspire Arizonans who care about protecting a livable climate and may be struggling to find hope in that effort. You can ask a question or nominate an unsung Arizona climate leader by filling out this form at https://forms.gle/QCCxBPSHGy1bUJQ99 or by emailing climate reporter Joan Meiners at [e-mail].
The price of gasoline is a frequent hot topic of conversation around the water cooler, er, gas pump. It also comes up like clockwork every four years during the run-up to the presidential election when it is, incorrectly, used to blame or praise candidates for their economic approach (turns out gasoline prices have very little to do with short-term domestic policies and are largely out of any sitting president's control, according to energy analysts).
In Arizona, gasoline tends to be a bit more expensive than the national average, as my colleague Russ Wiles reported recently in advance of Memorial Day weekend travel.
One reason could be that a state law requires the summertime use of a special blend designed to help control ozone and other air pollutants that peak during hot months in metro Phoenix, which consistently ranks among the regions with the worst air quality in the country. After Wiles' story was published, he received questions from readers about whether that requirement is still in place and, if so, whether it's worth the added cost.
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"Russ, unfortunately, you didn't mention the exotic blend of gasoline only Arizona is required to use to supposedly lower the ozone levels, which costs tons more than similar blends that could supposedly have the same effect on pollution and are cheaper," one reader wrote.
"You didn't mention the special blend that is required by the consent order locally signed," another reader pointed out. "Is it no longer in effect?"
Arizona's cleaner-burning gasoline blend was not the focus of Wiles' story last month. But since burning fossil fuels like gasoline for transportation is a top contributor to the emission of greenhouse gases causing the climate to warm and destabilize, and because ozone is an indirect part of that larger equation, it is the focus of this story — part of our monthly series answering reader's climate-related questions or highlighting a local climate leader. (Submit your question here: https://forms.gle/QCCxBPSHGy1bUJQ99.)
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The most basic difference with cleaner-burning gasoline is the addition of oxygen-containing compounds, or oxygenates, that help gasoline burn more completely in fuel tanks and not evaporate from vehicles. This makes for better fuel efficiency (with some minor mpg tradeoffs) while minimizing toxins that end up in the air.
CBG blends also reduce the amount of benzene, a known human carcinogen, by half and the amount of sulfur, which facilitates better emissions controls on vehicles, by up to 80%. And they typically cut back on the use of other smog-forming hydrocarbons once thought to improve vehicle performance. Extensive testing with millions of miles driven on CBG blends since 1996, however, has shown no negative effects on vehicles or in other types of gasoline-burning engines. The fuel types can be used interchangeably without any modifications.
The estimated effect is a 15% reduction in smog for a 5- to 15-cent per gallon cost increase. (These stats are for California, which has a slightly different blend. Arizona officials declined to comment for The Arizona Republic on how the local CBG blend differs or might affect prices.)
It's tough to translate that added cost at the pump into health care savings related to air pollution's links to higher incidences of asthma, heart disease, lung cancer, stroke and more. But since children can be especially vulnerable to air pollutants, the value of reducing them now can pay dividends for society further into the future, with incoming generations that are able to be more productive in the workforce and less reliant on the health care system.
More: Reader Q&A: How can I protect my kids from climate pollution and advocate for clean air?
Jeremy Martin, a chemist who directs fuels policy for the Union of Concerned Scientists' Clean Transportation Program, said it's important to look at vehicles and fuels as an interconnected system shifting with gasoline markets and vehicle efficiency improvements, and also with societal health outcomes and concerns.
"One important piece of context is that federal fuel regulations have been changing as well," Martin said. "Vehicle regulations and fuel regulations go hand in hand, and together they result in reduced air pollution and reduced health impacts from that pollution."
The American Lung Association reported in 2025 that Arizona ranked fourth in the number of unhealthy ozone days and that 84% of Arizonans live in communities with unhealthy air.
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Arizona's struggle with unhealthy air goes back decades, and so does its history of trying to contain it using cleaner-burning gasoline, one of several tools in the air quality arsenal.
It all started in 1997, when the U.S. Environmental Protection Agency extended its reformulated gasoline program to the Phoenix area to bring it into compliance with air quality regulations established by the Clean Air Act. Then-Gov. Fife Symington supported this solution and asked in January 1997 that the EPA require refiners to supply local retailers with the reformulated gasoline blend by June.
But in September of that year, Symington resigned from office over bank fraud convictions that were eventually overturned. His successor, Gov. Jane Dee Hull, requested an exemption from the EPA program just one week later. Although Phoenix was still considered a "serious ozone non-attainment area," the EPA granted this removal as of June 1998, one year after it had started, because Arizona had developed its own clean fuel program to reduce emissions of particulates and volatile organic compounds that contribute to ozone formation.
The specifics of that state program have shifted and been revised over the years, with some efforts to increase its benefits for air quality and other introduced legislation, including in the current legislative session, aimed at expanding what types of fuel can be considered clean enough or loosening regulations.
Vince Wolpert, who manages CBG compliance for the Arizona Department of Agriculture, said the current supply is sourced from refineries in California, New Mexico and Texas and brought into the state primarily by two pipelines, one from California and the other from New Mexico.
"As for how the Department of Agriculture became involved, the Office of Weights and Measures already regulated fuel quality and quantity," Wolpert said. "Therefore, the state legislature tasked our agency as the enforcement agency for the CBG program."
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Beyond the cost-saving benefits of slowing destructive atmospheric warming by reducing tailpipe emissions that increase greenhouse gas concentrations and worsen storms, the climate issue becomes involved in gasoline pricing when demand for CBG intersects with Arizona's growing electric vehicle industry.
"Of course, our best bet would be to invest more in transit and electric vehicles to make a difference for our air," said Sandy Bahr, director of the Grand Canyon chapter of the Sierra Club.
Since 2022, Arizona has become an "EV battery manufacturing powerhouse," with several large new facilities incentivized by clean energy tax credits tied to former President Joe Biden's Inflation Reduction Act. Hundreds of millions of investment dollars and thousands of jobs have flowed to the state as a result.
But the Trump administration's budget proposal currently under consideration by the U.S. Senate would repeal most of those funds, as well as a program offering average Americans up to $7,500 back on electric vehicle purchases. Advocates say this would devastate Arizona's clean energy economy and have hazardous consequences for energy access, air quality and health.
Some analysts further predict that a slowing of the American electric vehicle industry — one that forces more people into internal combustion vehicles despite globally increasing market demand for EVs — could put more pressure on gasoline supply chains, causing a greater increase in prices at the pump than any version of a cleaner-burning fuel program.
Joan Meiners is the climate news and storytelling reporter at The Arizona Republic and azcentral.com. Her award-winning work has also appeared in Discover Magazine, National Geographic, ProPublica and the Washington Post Magazine. Before becoming a journalist, she completed a doctorate in ecology. Follow Joan on Twitter at @beecycles, on Bluesky @joanmeiners.bsky.social or email her at [e-mail].
This article originally appeared on Arizona Republic: Do Arizona's fuel blends help air quality or reduce greenhouses gases?