Location and price drive gasoline sales, according to a new survey by the American Automobile Association. But an extensive study also conducted by AAA, reveals that consumers would be wise to factor the quality of the gasoline in their purchase decision.

Using an independent engine testing lab that specializes in fuel analysis, AAA sought to answer the question: Is “Top Tier” gasoline worth the price? The short answer is yes.  

Ford 2.3-liter engine tested on a dynamometer.
Ford 2.3-liter engine tested on a dynamometer.
Photo: AAA

What Is Top Tier Gas?

Gasoline is essentially a shared commodity, often stored in common containers until it is 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 dosage 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, eight automakers—Audi, BMW, Fiat Chrysler Automobiles, General Motors, Honda, Mercedes-Benz, Toyota, and Volkswagen—have united in support of Top Tier gas, specifically recommending it to their owners with the goal of preserving their engines’ original performance and emissions over time.

Top Tier retailers include 76, Aloha Petroleum, Amoco, ARCO, Beacon, BP, Break Time, Cenex, Chevron, CITGO, Conoco, Co-op, Costco, CountryMark, Diamond Shamrock, Entec, Esso, Express, Exxon, Holiday, Kwik Star Stores, Kwik Trip, Mahalo, MFA, Mobil, Ohana Fuels, Petro-Canada, Phillips 66, PUMA, QT, Quik Trip, Road Ranger, Shamrock, Shell / Shell V-Power, Sinclair Standard, SuperAmerica, SuperFuels, Tempo, Texaco, Tri-Par, and Valero.

Study Shows Top Tier Gasoline to Be Worth the Extra Price
Intake valve comparison showing a new valve compared to the results from the 100-hour engine test.
Photo: AAA

Gas Test Findings

For its test, the lab operated an engine continuously for 100 hours on a cycle to represent 4,000 real-miles of use. The engine was then disassembled, photographed, and its key components weighed and measured to determine the thickness of carbon deposits. Six fuels were used, randomly selected and split among three basic gasoline sources and three Top Tier.

The results showed that on average, Top Tier gasoline had 19 times fewer carbon deposits on injectors, intake valves, and in the combustion chamber when compared to regular gasoline.

AAA also found 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 three 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.

Given the technological trend toward more sophisticated engines, we think the EPA should consider raising the minimum detergent standards to ensure all drivers benefit from the type of performance and longevity promised by Top Tier fuels.