The national average price of a gallon of diesel was nearly unchanged from the previous week, according to weekly figures from the U.S. Department of Energy.

The DOE's Energy Information Administration reported Tuesday that the national average retail price was $2.931, down 7/10 of a cent from the previous week. That's 28.4 cents per gallon -- 10.7 percent -- higher than a year ago.

Prices remained over $3 a gallon in the Rocky Mountain, Central Atlantic and West Coast regions. The highest prices were reported on the West Coast, at $3.104 a gallon, up 3/10 of a cent from last week. The lowest average was seen in the Gulf Coast region at $2.876 per gallon.

The EIA also said that the national average price of retail gasoline (regular grade) was unchanged from last week, remaining at $2.682 per gallon. Gasoline prices are 3.6 percent higher than at this time last year.

Oil future prices for light, sweet crude were down 51 cents Tuesday, at $74.09 a barrel, on the New York Mercantile Exchange. An explosion at a refinery in Mexico sent oil prices higher near the end of the day, after dropping as low as $72.63.

The Wall Street Journal notes that U.S. commercial stockpiles of oil and oil products have risen to the highest levels in 27 years, and recent economic data haven't offered any signals that demand will grow fast enough to keep pace.