Camarillo, Calif. ? U.S. retail gas prices were down again in the last two weeks, shedding almost 8 cents a gallon, according to a survey released Sunday.

The national average for self-serve regular was about $2.20 on Oct. 20, compared to $2.28 from two weeks earlier, according to the Lundberg Survey of 7,000 gas stations across the country.

Mid-grade prices averaged around $2.31, while premium stood at nearly $2.42.

Gas prices have dropped more than 82 cents since Aug. 11.

The lowest average cost for a gallon of self-serve regular, $1.98, was in Tulsa, Okla., while Honolulu recorded the highest price, $2.84.