The average price of a gallon of on-highway diesel fuel was down slightly, continuing a six-week streak of decreases, according to the latest numbers from the U.S. Energy Department.

The national average dropped by 1.1 cents last week settling to a per gallon price of $2.832.  Compared with the same week last year, the price of a gallon is down $1.081.

Prices fluctuated regionally with some areas of the country actually posting slight increases. The largest decrease in price was in the Central Atlantic region, dropping by 2.1 cents while the largest increase in price was in the Rock Mountain region which was up .9 cents.

Prices of regular gasoline followed suit this week, posting a very slight drop of .8 cents to $2.793 per gallon nationally.

Prices were mostly down across the board regionally with the Gulf Coast seeing the largest decrease at 2.1 cents and the Rock Mountain Region taking the sole increase in per gallon prices by 1.9 cents.

Per-barrel crude oil prices hit three-month lows this week as the stock market felt the effects of Greece’s financial crisis, according to MarketWatch. Another factor in lower prices was a potential nuclear program deal between Iran and the West which could bring a new supply of oil to the market.