What's the Difference Between Regular and Discount Gas?

Oct. 29, 2005— -- The cost of gassing up is higher than ever these days, and one money-saving option may be to opt for generic gas rather than name brands.

Even though the average motorist with a mid-size car could save up to a $100 a year by filling up with generic, many people wonder about the quality of no-name brands.

At one station in Maryland, a Mobil station was charging $2.62 a gallon, 20 cents more than the generic Liberty station across the street.

A joint study by ABC News and the Maryland State Comptroller's Office examined the difference between name brand and generic gas. Chemists at the Maryland Fuel Testing Laboratory conducted a battery of tests: They verified that the gas was formulated correctly for the season, checked for contaminants like excessive sediments or diesel accidentally mixed with the gas, and they ran the gas through an elaborate engine to ensure that it was all the same 87 octane level.

Here's some good news for consumer: Regular and discount gas are basically similar.

"By and large, it's one and the same," said Bob Crawford of the Maryland Fuel Testing Lab. "You will find results will almost mirror each other. There are going to be slight variations, but gasoline is gasoline."

The primary difference between competing brands is the amount of detergent the distributors add to it. Even still, the difference is generally minor: The EPA requires all gas to have a minimum amount of detergent to keep a car's engine clean.

"You would be paying for brand loyalty, primarily," said Crawford, explaining why brand name gas costs more. "Some people feel more comfortable dealing with a particular brand."

Crawford, who has been studying fuel for 36 years, uses whatever gas is the cheapest. Some cars require premium gas, but generally, regular is fine.

Brands like Mobil and Sunoco keep their gas formulas secret, but Mobil says it adds at least twice the amount of detergent as generic gas, and that it adds the same amount to all three grades of gas.