Increased production at refineries and reduced demands makes buying fuel in Rocky Mountain region easier on the wallet.
The energy department forecast crude oil will average $102 a barrel next year.
Over the last three weeks, the national average retail price of diesel has climbed 17.1 cents.
The national average price fell 1.2 cents to $3.937.
All regions gained in price, led by a 3.6-cent jump on the Gulf Coast to $4.06.
The national average dipped 0.7-cent to $4.098, but remains $1.02 higher than a year ago.
Diesel prices averaged $2.98 a gallon last summer.
The national average price is 96.7 cents higher than the same week last year.
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