The price of diesel fuel fell by a small amount for the fourth straight week, maintaining a downward trending, but nearly-flat pattern for the past month, according to the Energy Department.  

The national average price of on-highway diesel fuel fell by 1 cent last week, settling at 2.389 per gallon at the pump. The price is a little more than 10 cents cheaper than it was in the same week in 2015.

Prices were down in all major regions with the largest price drops coming to the West Coast and Gulf Coast at 1.4 cents. The smallest drop in prices was in New England where diesel prices dropped by 0.5 cents.

Average prices for regular gasoline increased this week, jumping 2.3 cents to a per gallon price of 2.225 at the pump. Despite the increase, the price is still 10.2 cents cheaper than it was in the same week a year ago.

The largest price increase was in the Lower Atlantic region at 7.7 cents per gallon. The largest decrease in prices was in the Rocky Mountain region at 0.9 cents per gallon.

The rumored deal to freeze oil production between oil producing countries continues to affect the crude oil market with a slight increase in prices on Sept. 19, according to a MarketWatch report.

Venezuela recently indicated that a deal was likely to happen between oil producing nations, both in and out of OPEC that could have the effect of stabilizing the oil market. Venezuela has been hit hard by low crude oil prices in the past year. There are also conflicting reports that a firm deal was unlikely to happen soon. Prices were also affected by fighting in Libya which is delaying an expected increase in oil production for that country.