The average retail price of diesel fuel in the United States declined 1.3 cents per gallon to $1.488, the U.S. Department of Energy reported. Diesel fell 0.2 cent the week before, which followed a period of mostly rising prices since June 30, when commercial trucking's dominant fuel was $1.42, the lowest price so far this year. Last week's decrease would save truckers $2.60 on a 200-gallon purchase of diesel at retail pumps. The price is 9.2 cents higher than the corresponding week a year ago, DOE said. DOE also said the average price for regular gasoline fell 2.9 cents to $1.717 per gallon.Gasoline, used by about one-third of trucking, is down 3 cents since setting a record of $1.747 on Aug. 25.The price of diesel decreased throughout the country, with all of DOE's geographic regions reporting a decline of at least 0.7 cent. The West Coast saw the largest decrease, 4 cents, to $1.641.