Diesel prices across the United States plummeted 6.6 cents in the week ending Dec. 19, falling at the sharpest pace since May 2010 as crude oil prices inched up.

The average diesel price moved to 3.828 a gallon, up 58 cents from a year ago but down 29.6 cents from the 2011 high, the U.S. Energy Information Administration said. Prices were at their lowest in six weeks but were up 6.1 cents from 12 weeks ago.

California was the only region to see diesel stay at or above $4 a gallon mark, as prices in the East Coast’s New England and Central Atlantic regions fell below $4 for the first in five weeks. The Midwest saw the largest price decline, down 8.3 cents to $3.765 a gallon.

The average price has fallen 29.6 cents, 7.1 percent, since reaching its high point during the week of May 2 at $4.124 a gallon.

Crude oil for January delivery rose 35 cents to $93.99 a barrel on the New York Mercantile Exchange. Prices recovered from six-week lows after gains in equity markets.