The national average price of a gallon of unleaded gasoline fell 12.7 cents to $2.51 per gallon for the week ending Aug. 31, a move that brought it back to late-April levels, according to the U.S. Department of Energy.

The average price is now 94.9 cents higher than it was a year ago, after a week of sharp declines around the country in the nine regions tracked by the agency's information division.

The sharpest declines came in the Midwest where the gallon price fell 20.1 cents to $2.468 and on the West Coast, where it declined 12.1 cents to $3.162. The lightest decline came in the Rock Mountain region of 5.2 cents to $2.768.

Among states, California gave ground as the most expensive gasoline, falling to $3.346 behind Alaska's $3.40-per-gallon average. Nevada ($3.129) and Hawaii ($3.105) are the only other states with $3-per-gallon gasoline. At the other end of the spectrum, 28 states now have gasoline prices below $2.50 per gallon. South Carolina's $2.023 price remains the lowest in the nation.

Meanwhile, the average price of diesel fell 4.7 cents to $2.514. Diesel now costs $1.30 less than it did a year ago.