Photo via Wikipedia.

Photo via Wikipedia.

The national average price of gasoline fell 4.9 cents to $3.408 per gallon for the week ending Sept. 15, according to federal data.

A nearly three-month decline in gasoline prices has brought the average price to 13.9 cents lower than it was a year ago. For the week, the price of gasoline declined in nine of the nine regions tracked by the U.S. Energy Information Administration. The sharpest decline came in the Midwest, where the price fell 8.1 cents to $3.357 per gallon. Gasoline still costs the most on the West Coast, where it now averages $3.741 per gallon.

The average price of gasoline now costs at least $3.50 in 16 states and the District of Columbia, according to the AAA's Daily Fuel Gauge Report.

Meanwhile, the national average price of diesel fell 1.3 cents on the week to $3.801 per gallon. Diesel now costs 17.3 cents less than it did a year ago.