Diesel prices across the country rose over the past week to their highest average in nearly six months, the Department of Energy reported on Monday. The DOE's weekly price survey shows diesel just shy of four dollars at $$3.987 a gallon.

Diesel has crossed the four-dollar threshold in five of DOE's eight regional price surveys for the first time since mid-May. It is now more than 80 cents a gallon higher than this time a year ago.

Driving the current round of domestic price hikes are surging U.S. exports of diesel fuel. Fuel exports hit a new record in August at 895,000 barrels a day.

In 2003, U.S. refiners exported a little more than 100,000 barrels of fuel a day, primarily to Central America and South America, the federal Energy Department says. Since then, that figure has soared, reaching 656,000 barrels a day in 2010, marking a seventh straight record year. This year, export volume has moved further into record territory. It averaged 730,000 barrels a day through the first six months of the year.

Exports of U.S. refined fuels are only expected to increase, with global demand projected to rise sharply in the coming years.

Oil Weakens on Euro Debt Concerns while Libya Readies Oil Shipments

Meanwhile on oil markets Monday, benchmark crude gave up 85 cents to end the day at $98.14 per barrel in New York, as investors remain nervous that massive debt burdens in Greece and Italy will mean bank failures and perhaps another recession. On Friday, crude oil futures wound up the week at $98.99 a barrel on the NYMEX, their best performance since July.

In other oil news, Libya appears to be moving quickly to resume oil exports that are a key resource for European refineries. Oil officials in Libya say the country should be able to produce up to 700,000 bbl by the end of the year -- nearly half of what the country can produce. Production was all but shut down during the past several months because of unrest in the country.

Regional Retail On-Highway Diesel Prices
(Dollars per gallon, including all taxes)

New England: 4.030, Last week: +0.080, last year: +0.800
Central Atlantic: 4.085, Last week: +0.088, last year: +0.782
Lower Atlantic: 3.906, Last week: 0.090, last year: +0.773
Midwest: 3.987, Last week: +0.124, last year: +0.820
Gulf Coast: 3.882, Last week: +0.086, last year: +0.782
Rocky Mountain: 4.093, Last week: +0.115, last year: +0.815
West Coast: 4.171, Last week: +0.062, last year: +0.842
California: 4.270, Last week: +0.057, last year: +0.931

Canadian Average Diesel Prices, Week of Nov. 8
MJ Ervin & Associates conducts a weekly survey of retail diesel prices in about 60 different Canadian cities. The survey is made available here at approximately 3:00 pm Eastern Time on Tuesday each week.

High 143.4/L ($5.43 US gal) Whitehorse, Yukon
Low 119.9/L ($4.54 US gal) Edmonton, Alberta
Avg. 131.3/L ($4.97 US gal)
(U.S. prices do not include exchange)