As of Friday, a gallon of midgrade gasoline averaged about $2.66, and premium cost nearly $2.76, according to the survey of 7,000 gas stations across the country.

Nationwide, the highest average price for regular gas was $3.10 per gallon in San Francisco. The lowest, at $2.22 per gallon, was in Anchorage, Alaska.

Concerns over falling gasoline inventories from decreased refinery production and fewer imports have boosted oil and gasoline prices lately. On Wednesday, the government reported that total U.S. motor gasoline inventories fell by 3.8 million barrels to 216.4 million barrels, a sharper decline than the 1.4 million barrel drop that analysts had expected.