UPDATED--Despite a recent run-up in the price of oil, the average cost of diesel over the past week is unchanged but still at a five-month high, according to the U.S. Energy Department.

The $3.981 per gallon price follows three straight weekly hikes with diesel gaining 8.5 cents during the period, while the current price is 15.1 cents lower than the same time a year ago.

In the different regions of the country, diesel costs increased in about half and fell in the other half. The biggest hike is in the West Coast region, where it added 1.4 cents, registering $4.142, also making it the highest priced part of the country, while the largest drop is in the Lower Atlantic sub region of the East Coast, shedding 1.3 cents, for an average of $3.917 per gallon.

The lowest priced region for diesel is $3.898 in the Gulf Coast states, up 0.1 cent over the past week.

In contrast to diesel, the average cost of gasoline fell 2.1 cents to $3.587 per gallon, also 26 cents lower than the same time a year ago, its second straight weekly drop.

Gasoline prices fell in all parts of the country except in the Rocky Mountain and West Coast regions. It ranges from a low of $3.377 in the Gulf Coast states, a drop of 2.9 cents from last week, to a high of $3.797 in the West Coast, an increase of 4.7 cents during the same time. 

Crude on Monday fell from a 28-month high hit on Friday. It lost just over a dollar on the day, settling at $109.52 per barrel, which is about a dollar higher than the same time a week ago. The daily decline was due likely to less anxiety over talk about the U.S. possibly taking military action against Syria for the alleged use of chemical weapons against some of its civilians.

President Obama, who is pushing for the action, plans to take his case before the American public during a broadcast Tuesday evening while he has been working to convince lawmakers on Capitol Hill.

Update adds gasoline prices.