Fuel prices crept higher over the past week, according to the latest report from the Iowa Department of Agriculture and AAA-Iowa. As of Thursday, July 20, the price for a gallon of regular unleaded gasoline averaged $3.37, a four-cent increase from the prior week but still 87 cents lower than a year ago. Gas prices in Iowa remain 21 cents below the national average, which also jumped four cents to $3.58 per gallon. Retail diesel prices rose one cent to $3.60 per gallon, compared to $5.16 per gallon recorded a year ago. Nationally, diesel prices were 27 cents higher than in Iowa at $3.87 per gallon. Wholesale ethanol held steady at $2.16, while natural gas prices at the Henry Hub reporting site hiked 13 cents to $2.76 per MMBtu.