AAA study finds Top Tier gas brands offer big advantages

The ads at many gas stations are familiar: Retailers proclaim that their gasoline is a special, high-tech blend that offers all kinds of benefits.

Many talk about how their product is a “Top Tier™ gasoline,” which they say improves engine performance by reducing the amount of “gunk” left behind. AAA recently tested a number of Top Tier and non-Top Tier gasoline brands and found that, on average, Top Tier brands left 19 times fewer intake valve deposits. With Top Tier brands widely available and only costing about 3 cents more per gallon, AAA urges drivers to prioritize quality when deciding where to get gas.

What is Top Tier gas?

Top Tier gasolines contain special detergent additives to prevent the buildup of carbon deposits (known as gunk) in the engine. Engine deposits increase emissions, reduce fuel economy, and lead to other performance issues, which is why the Environmental Protection Agency mandates a minimum level of detergent.

Some automakers don’t think those standards go far enough, and they run a program called Top Tier that has developed more stringent guidelines. Today more than 40 retail fuel brands participate in the program and follow its detergent standards.

Are "premium" gas & Top Tier gas the same thing?

No. When gas stations separate their fuels into regular, mid-grade, and premium, they are referring to the octane rating. Fuels with a higher octane rating are required by some high-performance engines to prevent knocking or improve fuel economy, but being premium doesn’t have anything to do with the fuel’s detergent additives.

Many drivers understandably want to put the best gas in their car. But if your vehicle manufacturer doesn't recommend premium fuel, buying it can be an unnecessary expense. Read more about premium fuel.

Is Top Tier gas better for engines?

To see whether Top Tier detergents work as intended, AAA selected Top Tier and non-Top Tier gasolines from a southern Texas market that represent the gas sold in most of the country. Engines in a lab simulated 4,000 miles of driving with each fuel, and then were inspected for deposits.

The results: Top Tier fuels left engines much cleaner. On average, non-Top Tier fuels left 660 milligrams of deposits on each intake, compared to an average of just 34 milligrams for Top Tier fuels. That’s 19 times fewer deposits, or a reduction of almost 95%. Top Tier fuels also left fewer overall deposits throughout the engine.

Other Top Tier findings

Top Tier brands didn’t just keep clean engines clean. To see if they might also help remove deposits from dirty engines, AAA researchers took a high-mileage engine with substantial residue inside and ran it on Top Tier fuel for 1,000 miles. It was re-inspected, and researchers found that a significant amount of residue had cleared.

AAA also investigated whether these brands cost significantly more than others. Over a 12-month period, researchers found the average difference between Top Tier and non-Top Tier brands was just 3 cents per gallon.

Do drivers prefer Top Tier fuel?

Given that there appear to be real benefits to the Top Tier standard, AAA researchers commissioned a telephone survey to see if fuel quality was a top concern for American drivers, as opposed to convenience or price. The results:

63% of drivers

believe there is a difference in the quality of gasoline sold by different gas stations

34% of drivers

say they usually buy gasoline with an enhanced detergent additive like those in Top Tier gas

Drivers' top reasons for picking a gas station

Location

75%

Price

73%

Rewards program

29%

Gas has detergent

12%

AAA's advice for drivers

Use gas that meets Top Tier standards whenever possible

AAA’s tests demonstrate that Top Tier detergent gasoline is effective at combating carbon buildup. Not sure which brands have Top Tier gas? Check out a list of participating brands.

Shop around for gas with the Auto Club App

The extra cost of Top Tier fuels (generally a few pennies more per gallon) and occasional inconvenience are outweighed by the long-term fuel savings and performance benefits. Plus, with the new AAA App’s Cheapest Gas feature, finding a Top Tier gas station nearby is easy. Explore the free Auto Club App.

Don't assume it's too late to benefit from Top Tier gas

The results researchers got from running Top Tier gas through a dirty engine suggest that detergents can help clean out deposits, not just prevent them. Using Top Tier fuel for several fill-ups may yield improved performance.

Use the right fuel — don’t confuse “premium” with Top Tier

If the owner’s manual calls for premium-grade gas, that’s a reference to the octane rating, not fuel quality. Top Tier standards apply to all octane grades of fuel, whether regular, mid-grade, or premium.

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