The price of diesel fuel rose for the 15th week in a row to an average of $3.908 nationwide, according to the Department of Energy, but at a less-steep rate than the double-digit gains of the past two weeks -- 3.8 cents higher than last week and 98.4 cents higher than a year ago.

In some areas of the country, prices are over $4 per gallon, with the highest prices reported in the West Coast region at $4.091 average for the region and $4.17 in California. The lowest average price was in the Gulf Coast region at $3.842.

Diesel is at its highest since it late September 2008, when it was at $3.958 a gallon, on its way down from the record $4.764 per gallon set in July of that year.

Gasoline rose 4.7 cents to $3.567 a gallon, its 14th increase in 15 weeks.

Crude oil prices ended the day at $101.19 a barrel on the New York Mercantile Exchange after dropping below $99 earlier in the day. While the earthquake and tsunami in Japan caused oil prices to drop, once Japan begins to rebuild, demand for petroleum products is going to soar.

Japan has had to shut down its 10 nuclear reactors, which generated 11 percent of its power, in the wake of the earthquake. The general expectation is that Japan will compensate by relying more on traditional fossil fuels, such as coal, natural gas, and oil. One analyst said Japan could boost crude oil imports by about 300,000 barrels per day. It also may look to import refined fuels, such as diesel, from the U.S. and India.