U.S. diesel price sets record again, California hits $5 The national average retail price of a gallon of diesel soared 22.6 cents to yet another new record high of $4.723 for the week ending Monday, May 26. The price -- which has climbed 76.8 cents in the last seven weeks -- is $1.906 higher than the same week last year, according to the U.S. Department of Energy. The 22.6-cent increase is the third-highest single-week price increase since the Energy Information Adminstration began keeping figures; No. 1 was the week immediately following Hurricane Katrina. The second-biggest single-week spike followed about a month later in the wake of Hurricane Rita. Out of the Top 10, six are from 2008 -- with No. 3-5 coming during May alone. There have been only 20 double-digit single-week increases, and nine of them have occurred this year. The average U.S. price now has been above $4 for seven weeks. DOE's weekly roundup of the nation's diesel prices was delayed one day because of the Memorial Day holiday. All regions tracked by DOE saw price increases. The largest increase by region, 27.3 cents, was found on the West Coast, where week-over-week prices rose to $4.883. The smallest price increase by region, 20.4 cents, was found in the Midwest, where week-over-week prices climbed to $4.667. The nation's most expensive diesel by region, $4.913, was found in the Central Atlantic, where prices soared 23.1 cents. California, which DOE tracks separately, recorded the nation's first-ever $5 diesel price, $5.027; prices in that state rose 29.0 cents last week. The nation's least expensive diesel by region, $4.653, was found in the Rocky Mountains, where prices climbed 21.1 cents.