The national average price of a gallon of diesel rose 5.4 cents from last week, to $3.069, according to weekly figures from the U.S. Energy Information Administration.

Last week was the first week diesel had topped $3 a gallon since November 2008. Unlike last week, this week the average was more than $3 in every region.

This week's average is 84 cents per gallon higher than the year-ago price. The highest average price was seen in the West Coast, at $3.187, followed closely by the Central Atlantic at $3.186. The lowest prices were reported in the Gulf Coast region at an average $3.023.

Although crude oil prices dropped a bit Monday, settling at $84.34 a barrel, they're still 69 percent higher than the same time last year.

According to published reports, Monday's drop is likely due to a weaker U.S. dollar compared to the Euro. The dollar fell over the weekend after the European Union pledged nearly $40 billion to help Greece with its fiscal problems.

There's also a possibility that recent forecasts of a worse-than-average hurricane season could be spurring thoughts of a possible disruption of oil from Gulf platforms.

Tom Kloza with Oil Price Information Service, predicted several weeks ago on his blog, "Speaking of Oil," that we would see U.S. oil and fuel prices hit 18-month highs in the coming weeks, meaning $3 per gallon or higher for retail gasoline and retail diesel and in the mid-$80's for crude oil. He told Truckinginfo Monday, "I think we'll see just a little bit more excess and then a bit of a correction. Happens every spring, and happened a little earlier this year."