The national average price of a gallon of unleaded gasoline increased 5.8 cents to $2.30 for the week ending May 23, according to federal data.

The national average price is now 47.4 cents lower than a year ago, after falling in nine regions tracked by the U.S. Energy Information Administration. The Midwest saw the sharpest increase of 10.2 cents to $2.28, while the Gulf Coast average increased 7.7 cents to $2.064. West Coast gasoline remained essentially flat with a 1.4-cent increase to $2.658.

Among states, four now have an average price above $2.50 per gallon, including California ($2.804), Hawaii ($2.671), Alaska ($2.589), and Washington ($2.589). All states now have an average price of at least $2 per gallon with Mississippi ($2.056) now the lowest price, according to the AAA's Daily Fuel Gauge Report.

Meanwhile, the national average price of diesel fuel increased 6 cents to $2.357. Diesel is now 55.7 cents lower than it was a year ago.