After several weeks of drops, the national average price of diesel rose for the week ending May 30, according to the U.S. Department of Energy.

For that week, the national average checked in at $2.16 per gallon, up less than a penny from $2.156 per gallon the week before. That’s 41.4 cents higher than the average for the same time period in 2004.

The biggest increase was in the Lower Atlantic region, where prices rose 1.5 cents to $2.119 per gallon. The East Coast overall saw a slight rise to an average of $2.188 per gallon. New England averaged $2.32 per gallon, while the Central Atlantic region posted an average of $2.284 per gallon.

The Midwest posted the second biggest increase of the week, with prices rising 1.4 cents to $2.111 per gallon. The Gulf Coast had a slight increase, rising to $2.117 per gallon.

California’s average price, meanwhile, continued to slide, falling less than a penny to $2.367 per gallon.

Decreases were logged in the Rocky Mountain region and along the rest of the West Coast. The average price in the Rocky Mountain area fell 2.8 cents to $2.179 per gallon, while the West Coast fell $2.2 cents to $2.317 per gallon.

Oil prices, meanwhile, dropped slightly after hitting a high of $52 per barrel on Tuesday, May 31.

Analysts expressed surprise that prices were not spiking higher on signs of increasing global demand and the potential for insufficient supplies.

With the U.S summer driving season in full swing, however, demand is only expected to increase.

The Organization of Petroleum Exporting Countries is expected to meet in mid-July to decide whether or not to cut output levels.