This story is part of The Salt Lake Tribune’s ongoing commitment to identify solutions to Utah’s biggest challenges through the work of the Innovation Lab.

Six years after Gov. Gary Herbert and the Utah Legislature worked out an incentive deal to encourage Utah’s gasoline refiners to update their plants to produce cleaner Tier 3 gasoline, four of five Utah refiners are producing and selling the cleaner fuel.

Utah’s population is concentrated in the valleys of the Wasatch Front, where pollutants are trapped by climate conditions to produce some of the dirtiest air in the nation.

With about half of those pollutants generated by transportation, low-sulfur fuels are considered a significant fix. In 2019, Herbert urged Utahns to fill up only at stations selling Tier 3, noting that the gasoline produces 80% less pollution in newer cars.

“It’s like taking four out of every five cars off the road,” he said.

The fifth refiner, Big West Oil in Woods Cross, has not filed for the “High Infrastructure Tax Credit,” according to the Utah Office of Energy Development, which is charged with verifying that refiners have lowered the sulfur level in their gasoline to at least 10 parts per million, the federal standard for Tier 3 fuels, but the company can still file for and receive credits when it has met the sulfur requirement.

“Big West Oil is compliant with the EPA Tier 3 fuels standard at our NSL facility,” said Mike Swanson, president of Big West’s refining division. “We remain committed to deliver 10 ppm sulfur gasoline to the Utah market by 2024, a commitment the company made to the House Natural Resources, Agriculture, and Environment Committee in January of 2020.”

Big West refines roughly 35,000 barrels of oil per day, making it the second smallest Utah refinery. It is managed by a holding company, Salt Lake City-based FJ Management, which also controls the Maverik chain of convenience stores. That chain includes 380 stores across 12 western states. Big West gasoline is sold in Maverik stores and elsewhere.

“Maverik is meeting the requirements for Tier 3 fuels,” said Michelle Monson, communications & corporate social responsibility director. “Maverik always has and will continue to comply with all environmental regulations and our approach to Tier 3 is no different. The fuel that Maverik sells to consumers in Utah is purchased from refiners that are compliant with all government standards and regulations.”

Utah Division of Air Quality Director Bryce Bird doesn’t doubt that Tier 3 fuels are improving the air in Utah, but he said it’s hard to pinpoint how much since they haven’t been widely available for very long. “We are unable to attribute changes in air quality in short-term trends to any specific strategy. It is always a combination of many factors.”

As defined by the U.S. Environmental Protection Agency, Tier 3 gasoline contains less than 10 parts per million of sulfur, a considerable reduction from the previous Tier 2 standard of 30 ppm.

How does Tier 3 improve the air?

Removing sulfur extends the life and effectiveness of catalytic converters in cars. The converters produce cleaner exhaust by removing nitrogen oxides and by oxidizing residual hydrocarbons (unburned gas). The sulfur in gasoline builds up on the converters and reduces their effectiveness. The fuel is most effective in cars sold since 2017, which run as much as 80% cleaner with Tier 3 gas, but even older cars run 15% cleaner.

The EPA gave a 2020 deadline for smaller refineries like those in Utah to convert to producing Tier 3 fuels, but it also allows refiners to purchase credits from other refiners to comply. In essence, refiners who make gasoline that is below 10 ppm can get credits for being below the standard, and they can sell those credits to other refiners who are above that standard.

But to qualify for the state High Cost Infrastructure Tax Credit, which is expected to save refiners millions of dollars on their upgrades, they must hit the Tier 3 level on average in their gasoline. They can’t buy credits to make up the difference.

“The refineries were ahead of their time in voluntarily making the significant investments to produce tier 3 fuels,” said Jon Ekstrom, spokesman for the Utah Petroleum Refiners Association. He noted the clean air benefits will continue to improve as car standards improve through 2025.

Utah has five gasoline refineries north of Salt Lake City that produce most of the gasoline consumed in the state. The two largest, Chevron and Marathon, have been producing and selling Tier 3 gasoline since 2019. The next largest, HF Sinclair, says it has been producing gasoline below Tier 3 (7-8 ppm sulfur) since October 2021.

The smallest refinery, Silver Eagle, has always made low-sulfur gasoline because it relies on low-sulfur waxy crude from the Uinta Basin for its feedstock.

As of last month, Big West had not applied for the High Cost Infrastructure Tax Credit, according to the Utah Office of Energy Development, but there is no deadline for applying.

The energy office is tasked with verifying that refiners are producing fuels that are low enough in sulfur to qualify for the credits, and for that they rely on refiners’ reporting to the EPA. Refiners are required to submit reports from outside auditors showing the average sulfur content in their fuels.

EPA does not make those reports public. “Details related to production processes and other types of decisions made by industries and commercial enterprises are considered confidential in nature,” said Rich Mylott, EPA spokesman. All Utah refineries are complying with EPA rules, but they can do so by producing fuel above Tier 3 sulfur levels and buying credits.

Where do you find Tier 3 gas?

Meanwhile, it’s not always apparent whether a gas station sells Tier 3 gas.

“I hope that all the refineries will make that commitment to clean up our air,” said Salt Lake County Council member Suzanne Harrison. Harrison was a Democratic state representative when she launched a website back in 2020, Tier3gas.org, to tell drivers where they can buy it.

In general, the large brands (Chevron, Speedway, Sinclair, Exxon, Shell, Texaco) all sell it, and many of those rely on long-term contracts with the refineries. But smaller operators often rely on “rack” sales, buying from the refineries and paying spot prices. Price sensitivity can send them to different refineries.

Harrison, an anesthesiologist and longtime clean air advocate, has maintained the site herself, relying on retailers to report. In general, there hasn’t been much updating to the site. Most of the big chains sell Tier 3.