CLEVELAND - A 5 On Your Side investigation reveals how to get more of your money's worth at the pump.
Working with our partners at Scripps Howard News Service, we found the amount of detergents in gasoline varies among eight national brands.
Detergents are additives that keep your engine clean. Some experts believe more detergents can improve your vehicle's gas mileage.
In our test of regular unleaded gas, Exxon had the highest level of detergents, with 20 milligrams of residue per 100 milliliters.
BP and Shell followed close behind.
Marathon, Citgo, Pilot and Speedway samples each had less than half the amount of detergent found in the top three brands.
In our test of premium gas, Shell leads the pack with 31 milligrams.
BP and Exxon followed Shell.
The lowest levels of additives were found at Speedway, Mobil, Citgo, Marathon and Pilot.
Pilot's 8.8 milligrams was three times less than Shell's.
The Environmental Protection Agency requires gas companies to add detergents to gasoline.
In a statement, Pilot's Vice-President Alan Wright, said, "Our gas blends meet EPA requirements. We don't put in extra."
To test the gasoline, NewsChannel5 collected one gallon samples of regular and premium fuel.
The samples were tested by Paragon Laboratories, an independent, certified testing facility near Detroit.
Paragon performed unwashed gum tests. It is the same test automakers use when spot-checking gas to see if it meets their standards.
Scientists boiled each sample and measured the residue left behind. Higher amounts of residue mean there are higher amounts of detergents in the gasoline. Some experts say the higher level of detergent could equal better gas mileage.
"Obviously, the more detergent, the more efficient job it's going to do of cleaning the valves," said Tony Molla, vice president of communications for the National Institute for Automotive Service Excellence.
Molla said repeatedly filling up your vehicle with gas that does not have enough detergent could cause deposits to build up on your engine, which would cause 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," he said.
Molla said drivers who own newer cars should check their owner's manual for recommendations on the best gas for their cars.
He said all drivers should choose one brand of quality gasoline and stick with it.
"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 Molla.