An analysis by AAA reveals that gas with detergent additives can keep an engine running smoothly By Jeff S. Bartlett Not all gasoline is created equal. There’s plain old regular, and then there’s regular gasoline that meets a higher standard, known as Top Tier gas. The difference between the two is significant, based on an extensive study conducted by AAA. Its testing revealed that consumers would be wise to factor the quality of the gasoline into their purchase decision, even if it costs a little more. What Is Top Tier Gas? Gasoline is essentially a shared commodity, often stored in common containers until it’s purchased by a major retailer. After that, the retailer treats the gas with a specific additive, thereby giving the fuel its brand identity. But are these additives just a dose of marketing hype? Top Tier gasoline was developed in 2004 to go beyond the minimum standard for detergent additives to better protect increasingly sophisticated engines from carbon buildup and deposits on the intake valves, which can result in a rough idle, acceleration hesitation, knocking/pinging, and reduced fuel economy. Over the past 20 years, engines have become far more precise, operating under tighter tolerances and at higher compression ratios, while targeting cleaner emissions and improved fuel economy. To achieve these goals, several major automakers—Audi, BMW, Ford, General Motors, Honda, Mercedes-Benz, Subaru, Stellantis, Toyota, and Volkswagen—have united in support of Top Tier gas. Most specifically recommend it to their car owners with the goal of preserving the engine’s original performance and emissions over time. (Learn who owns which car brands.) Keeping things simple for consumers, when a participating retailer sells Top Tier fuel, all octane grades from regular to premium gasoline and diesel must adhere to the Top Tier standards. So it’s not necessary for drivers to upgrade to premium to gain the cleansing benefits. A Ford 2.3-liter engine being tested with a dynamometer. Top Tier Gas Retailers These are among the dozens of brands that sell Top Tier gas. See a full list of Top Tier retailers. 76 Mobil Aloha Petroleum Morongo Travel Center Arco Mountain Sky Travel Centers Beacon Ohana Fuels Cenex Pahvant Travel Plaza Chevron Phillips 66 Citgo QT/Quik Trip Conoco Ranger Fuel Costco/Kirkland Signature Gasoline Reeders CountryMark Rutter's Diamond Shamrock Shamrock Express Mart Shell Exxon Simonson Fast Fuel Sinclair Harmons Fuel Stop Sunoco Hele Texaco HFN - Hawaii Fueling Network Valero Holiday Value America Marathon Waterway Fuels Mega Saver Win Win Meijer WOW Top Tier Gas Test Findings For the test, an independent engine testing lab that specializes in fuel analysis operated an engine continuously for 100 hours on a cycle to represent 4,000 real miles of use. The engine was then disassembled and photographed, and its key components were weighed and measured to determine the thickness of carbon deposits. Six fuels were used and randomly selected and split among three basic gasoline sources and three Top Tier. Intake valve comparison showing a new valve with valves after a 100-hour engine test. The results showed that, on average, non-Top Tier gasoline left 19 times more carbon deposits on injectors and intake valves and in the combustion chamber than Top Tier gasoline had. AAA also found that Top Tier gasoline can have a cleansing effect, reducing intake valve deposits by 45 to 72 percent when used over a 5,000-mile interval. Variation in the results is attributed to the detergents used by different brands. Further, analyzing gas prices over a 12-month period found just a 3-cent price difference between non-Top Tier and Top Tier gasoline. Bottom line: For the nominal investment, this study shows that motorists would benefit from using Top Tier gasoline as their primary fuel. Consumer Reports is an independent, nonprofit organization that works side by side with consumers to create a fairer, safer, and healthier world. CR does not endorse products or services, and does not accept advertising. Copyright © 2025, Consumer Reports, Inc.
