(NAFB.com) – For the fourth straight week, the nation’s average price of gasoline has gone up, rising 8.7 cents from a week ago to $3.26 per gallon. The national average is up 16.7 cents from a month ago but 11.6 cents per gallon lower than a year ago. The national average diesel price increased 10 cents last week and stands at $4.09 per gallon—38 cents lower than one year ago. GasBuddy’s Patrick De Haan says, “One of the most critical elements to how much gas prices will climb is how quickly and effectively refiners can finish their pre-summer maintenance, start producing EPA-mandated summer gasoline, and build up supply of it before Memorial Day.” The price of oil has seen some sideways movement, but overall strength continues, with oil now closing in on $80, its highest level since November. Meanwhile, U.S. retail gasoline demand saw an increase of 0.7 percent for the week ending February 18.