PORTLAND, Ore., – New testing from AAA has uncovered significant differences in the quality of gasoline sold at fuel retailers in the United States. The independent laboratory testing compared gasolines that meet TOP TIER™ standards with gasoline brands that do not participate in the automaker-backed program. The research finds that consumers can clog their cars’ engines by not using gasoline with enough added detergents.

Among brands tested, non-TOP TIER gasolines caused 19 times more engine deposits than TOP TIER brands after just 4,000 miles of simulated driving. Such carbon deposits are known to reduce fuel economy, increase emissions and negatively impact vehicle performance, particularly on newer vehicles.

AAA Fuel Quality Research

The TOP TIER program and performance standard were developed to guarantee that participant’s’ gasoline meets stricter standards for engine cleanliness. TOP TIER gasolines are often marketed to consumers as having enhanced, engine-cleaning detergent additives.

To protect vehicle investments, AAA urges drivers to use a gasoline that meets TOP TIER standards for engine cleanliness and performance.

“AAA was surprised to learn the extent to which detergent additives impact gasoline quality,” says John Nielsen, AAA’s managing director of Automotive Engineering and Repair. “As advertised, tested TOP TIER gasolines kept engines remarkably cleaner than other fuels we tested.”

In response to increasing levels of carbon deposits in modern engine designs, the Environmental Protection Agency mandated a minimum level of detergent for all gasoline sold in the United States in 1996. However, some automakers believe the minimum does not go far enough to ensure optimal vehicle performance and their ability to meet increasingly-stringent fuel economy and emissions requirements.

“By selecting a quality gasoline, drivers can minimize engine deposits, increase vehicle performance and improve fuel economy,” says Marie Dodds, Public Affairs Director for AAA Oregon/Idaho.

AAA recommends:

  • Selecting a gasoline that meets TOP TIER standards
  • Following your vehicle owner’s manual and use the correct fuel for your vehicle. Many consumers associate fuel quality with the octane of the fuel (regular vs. premium), which is incorrect.
  • If you experience a rough idle, especially when the engine is cold, or hesitation during acceleration, it might be caused by the quality of fuel. Try changing to a TOP TIER gasoline for several fill-ups.
  • Shop around. TOP TIER fuel is only an average of three cents more per gallon. Drivers can find current gas prices along their route with the free AAA Mobile app for iPhone, iPad and Android. Learn more at AAA.com/mobile.

 AAA Fuel Quality Research

AAA Survey on consumers’ gasoline preferences:

Americans value convenience and price over quality when it comes to selecting a gas station.

  • Two-thirds (63 percent) of U.S. drivers believe there is a difference in quality of gasoline sold by different gas stations
  • Only one-third (34%) of U.S. drivers usually buy gasoline that contains an enhanced detergent additive.
    • Nearly half (47 percent) do not buy gasoline with an enhanced detergent additive.
    • 18 percent don’t know if the gasoline they usually buy contains an enhanced detergent additive.
  • The primary reasons U.S. drivers choose a gas station are:
  1. Location (75%)
  2. Price (73%)
  3. Rewards program (29%)
  4. Gas that contains a detergent (12%)
  • Baby boomers (41%) are more likely to buy a gasoline that contains an enhanced detergent additive than millennials (32%).
  • Men (44%) are more likely to buy a gasoline that contains an enhanced detergent additive than women (26%).

AAA recommends consumers research the fuel options near them. According to TOP TIER, one-third of gas stations meet the TOP TIER standard for fuel quality.

“The good news is consumers can reverse some engine deposits simply by switching gasoline brands,” says Steve Fox, Automotive Services Director for AAA Oregon/Idaho. “Performance issues such as rough idling or hesitation during acceleration can often be resolved after a few thousand miles with TOP TIER gasoline.”

AAA Fuel Quality Research

For testing purposes, AAA selected TOP TIER and non-TOP TIER gasolines from a southern Texas market that represents the type of gasoline sold across the majority of the United States. To measure intake valve and combustion chamber deposits, AAA engaged the services of an independent International Standards Organization 17025 certified engine testing lab to perform an American Society for Testing and Materials standard test on fuels.

Research methodology:

To evaluate consumer gasoline preferences, AAA contracted with a national research company to perform a telephone survey of 1,002 adults (18 years of age and older) living in the continental United States. Survey results are an accurate representation of the total continental U.S. population, 18 years of age and older, with a margin of error of +/- 3.1 percent at a 95 percent confidence level.

For additional information about fuel quality, including the full test report and fact sheet, visit NewsRoom.AAA.com.

As North America’s largest motoring and leisure travel organization, AAA provides more than 56 million members with travel, insurance, financial and automotive-related services. Since its founding in 1902, the not-for-profit, fully tax-paying AAA has been a leader and advocate for the safety and security of all travelers. Motorists can map a route, identify gas prices, find discounts, book a hotel and access AAA roadside assistance with the AAA Mobile app for iPhone, iPad and Android. Learn more at AAA.com/mobile. AAA clubs can be visited on the Internet at AAA.com.


AAA news releases, high resolution images, broadcast-quality video, fact sheets and podcasts are available on the AAA NewsRoom at NewsRoom.AAA.com.