What's in your gas tank?

There's no question… gas prices are high across the board, but we wondered what you get for your money at certain stations.

Detergent is one chemical that you pay for in all gasoline, regardless of cost and brand. The environmental protection agency requires it to be in our fuel to help prevent carbon buildup in cars. But it's also causing controversy among refiners, auto makers and fuel experts. Many say the EPA's minimum detergent requirement is extremely low and outdated.

We questioned how much detergent you get across various brands.

Working with our partners at the Scripps Howard News Service, we collected one-gallon samples of regular unleaded and premium fuel from eight national brands across three states. We took our samples to Paragon Laboratories, an independent, certified testing facility near Detroit to find out if all brands are created equal when it comes to detergent.

"One of the worst things you can do is to go from brand to brand to brand, getting the cheapest stuff you can find," said Tony Molla with the National Institute for Automotive Service Excellence

Molla says if you repeatedly fill up with gas that doesn't have enough detergent, deposits can build up causing your engine to burn more gas.
"As the deposits build up, they tend to attract more deposits - so it's very much like a process that the longer it goes untreated, the worse it becomes."

Paragon performed unwashed gum tests - the same test automakers use when spot-checking to see if gas meets their standards. Scientists boiled each sample and measured the residue left behind - the more residue - the more detergent - which could equal better gas mileage.

In our test of regular unleaded gas, Exxon had the highest level of additives, with 20 milligrams of residue per 100 milliliters. BP and Shell followed close behind, while Marathon, Citgo, Pilot and Speedway samples each had less than half the amount of detergent found in the top three brands.

"Obviously the more detergent, the more efficient job it's going to do of cleaning the valves, explained Molla.

While it may always be about price or convenience to many out on the road, it's also important to remember that consistency matters.

"We always recommend that you try to find one brand of gasoline that you like and stick with it or at least one location."

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