The national average price of diesel fell nine-tenths of a cent to $3.93 per gallon for the week. Diesel costs 4.5 cents more than it did a year ago, according to federal data.

While the national average price of gasoline continued its sideways trend, rising nine-tenths of a percent to $367 for the week ending May 26, it is just 2.9 cents higher than it was a year ago according to the U.S. Energy Information Administration.

For the week ending with the Memorial Day holiday, gasoline prices rose in four of the nine regions tracked in the federal data. The steepest rise came in the Midwest, where the price rose four cents. The average price of regular unleaded costs at least $3.50 in 34 states, according to the AAA's Daily Fuel Gauge Report.