For the fourth straight week, the average national price for a gallon of diesel fell - this time by a whopping 11 cents, to $2.857, for the week ending Sept. 10, according to the Energy Information Administration.
The price fell most dramatically in the Midwest -- 15 cents to $2.787. In California, where diesel retailers were required to switch to ultra-low sulfur diesel, prices declined five cents to $3.125.
Despite an 8.2-cent drop, the Rocky Mountain region remained the most expensive region at $3.236. The cheapest was in the Lower Atlantic region at $2.757, after a 9.3-cent drop.