The national average cost for diesel rose slightly for the week ending Oct. 24, according to the U.S. Department of Energy.

At $3.157 per gallon, the national average was less than a penny higher than the week before, but still more than 94 cents higher than the same week in 2004.

The Midwest had the highest prices, jumping 9.1 cents to $3.235 per gallon. The Rocky Mountain region was close behind at $3.232 per gallon.

Most other regions reported drops in prices. The East Coast fell 6.5 cents to $3.051 per gallon. The Lower Atlantic was the highest within that region at $3.115 per gallon. New England and the Central Atlantic states each came in at less than $3, with $2.873 and $2.940 per gallon, respectively.

California actually posted below the national average, at $3.152 per gallon, while the rest of the West Coast came in at $3.142 per gallon.

The Gulf Coast posted an average of $3.146 per gallon.

Meanwhile, the gap between the cost of diesel and the cost of gasoline continues to grow, reaching more than $1 in some places.

Jake Bournazian, an economist with the Energy Information Administration, told Land Line part of the reason for this is simple supply and demand.

“Supply conditions for diesel fuel are a lot tighter than gasoline,” he said. “Also, we are in the high demand period for diesel. Once you cross over into the heating season after Oct. 1, demand for diesel fuel increases and pretty much stays at a higher level through March.”

Bournazian said refineries that were shut down in the Gulf Coast region following Hurricanes Katrina and Rita are also a contributing factor.

“Refineries that were shut down along the Gulf Coast are mainly diesel producing refineries,” he said. “The market lost about 600,000-700,000 barrels of diesel production per day when those were shut down.”

Bournazian said diesel prices should come down somewhat when those refineries reach full capacity again, sometime in December. However, he cautioned that high prices would likely remain throughout the winter and could go even higher if there are further disruptions.