The average price of diesel fuel in the United States declined 5.4 cents a gallon to $2.561, the Department of Energy reported Aug. 24. The decline is the 13th consecutive weekly drop. The cumulative value of the 13-week falloff is worth 35.3 cents since May 25. The price of diesel is comparable with what it was in October 2009. The national average for trucking’s main fuel was cheaper by $1.260 a gallon from a year ago, DOE’s Energy Information Administration said after its weekly survey of fueling stations. Retail prices for the fuel declined in all major regions of the country. The largest decline was an 8-cent drop on the West Coast, excluding California. Gasoline declined 7.9 cents to $2.637 a gallon. The drop follows an 8.7-cent increase the prior week that had been the first rise in five weeks. The price of gasoline declined in every region of the country, falling 8 cents in the West Coast, the largest regional drop. West Texas Intermediate for October delivery dropped $2.21, or 5.5%, to close at $38.24 a barrel on the New York Mercantile Exchange on Aug. 24. It was the lowest settlement since Feb. 18, 2009. Prices have decreased the past eight weeks, the longest retreat since 1986, Bloomberg News reported. Oil’s worsening global surplus has driven prices down by more than 30% since May. Iran aims to expand its share of output in OPEC, while America’s crude supplies are almost 100 million barrels above the five-year seasonal average, according to Bloomberg. “We’re about 1.5 million barrels a day oversupplied right now,” Paul Sankey, an energy analyst at Wolfe Research, said on Bloomberg Radio. The Saudis would have made cuts to balance the market in the past but now “they are worried about Iran.”