The national average price of gasoline continued its nearly two-month decline, falling 3.3 cents to $3.472 for the week ending Aug. 18, according to federal data.

The price of gasoline is now 7.8 cents lower than it was a year ago, reports the U.S. Energy Information Administration. During the week, the price fell in eight of the nine regions tracked by the agency. The sharpest fall came in the Midwest, where the price fell 5.6 cents to $3.395. The price rose six-tenths of a cent in the Rocky Mountain region.

The average price of a gallon of regular unleaded now costs at least $3.50 in 21 states and the District of Columbia, according to AAA's Daily Fuel Gauge Report.

Meanwhile, the national average price of diesel fuel fell eight-tenths of a cent to $3.835 for the week. Diesel is now 6.5 cents lower than it was a year ago.