Generic vs. Brand-Name Gas: Are They Different?

March 24, 2007 — -- The average price of regular gas this week is $2.57 -- lower than a few weeks ago, but still far more than Americans are used to paying. As some drivers turn to generic gasoline from no-name stations to cut costs, "Good Morning America" investigated whether generic gas is good for your car.

With the help of the Maryland State Comptroller, ABC News compared gas from a name-brand Mobil station and a generic Liberty station right across the street from each other. Mobil was charging $2.69 a gallon for regular, while Liberty charged $2.49 a gallon.

The comptroller's office collected samples of regular unleaded at each station. The inspector followed a strict protocol, flushing the line between samples and carefully labeling canisters.

At the Maryland Fuel Testing Laboratory, chemists conducted a battery of tests. First, they verified that gas was formulated correctly for the season. Then, they checked for contaminants, like excessive sediment or diesel, accidentally mixed with the gasoline.

They also ran the gas through an elaborate engine to make sure it got the 87 octane level people pay for. Both samples easily met state standards.

"By and large, it's one and the same. … You will find results will almost mirror each other," said Bob Crawford, who works at the lab. "There are going to be slight variations -- but gasoline is gasoline."

When gasoline arrives at regional distribution centers, it's all the same. Different gas station chains then buy the raw fuel and add their own blend of detergents. In the past, there might have been more of a difference between different brands of regular unleaded, but these days the EPA requires that all gas contain a minimum amount of detergent to keep car engines clean.

If you're paying for a particular brand of gasoline, "you would be paying more for brand loyalty, primarily," Crawford said. "Some people feel more comfortable dealing with a particular brand."

Many customers keep coming back because they use a particular name-brand station's credit card.