Diesel prices in the U.S. have fallen for the fifth straight week. Can you say “Hooray!”? Back during the week of August 31, the average price of diesel was $2.64 per gallon; this week, it’s $2.58. Almost exactly a year ago, prices were just coming down from the highs of summer, dropping to $3.87 per gallon. Doing the math, current prices ring up at $1.29 less than a year ago.

Diesel prices are actually down across the board, with all nine regions of the country showing declines. The Gulf Coast region has the least expensive fuel at $2.51 per gallon, while the price of diesel is highest on the West Coast at $2.72.

Fortunately, it doesn’t look like there will be any surprises for the rest of the year, according to the Department of Energy. In its monthly short-term energy outlook, the DOE said the price of diesel will average $2.60 in the fourth quarter of 2009 ¾ pretty much what it is now.

To put prices in even more perspective, the national average cost of diesel has plummeted by almost 50% since July 2008, when it peaked at more than $4.70 gallon. Most likely agree though that the roller coaster isn’t over in the long-term ¾ that prices are still volatile, and will go up again, especially when the economy gets back on its feet. The DOE is already projecting prices to average up slightly to $2.78 per gallon in 2010.

What are your thoughts on current diesel prices? Do you agree they’re reasonable?