Iowa motorists are seeing moderate dips in fuel prices as the summer driving season begins in earnest, according to the latest report from the Iowa Department of Agriculture and AAA-Iowa. As of Wednesday, May 31, the price of regular unleaded gasoline averaged $3.37 per gallon across the state, a four-cent decrease from last week and 89 cents lower than a year ago. The national average climbed two cents on the week to $3.58 per gallon. Retail diesel in Iowa was down three cents to a $3.70 per gallon average, compared to $5.16 per gallon a year ago. Local prices remain 25 cents below national averages, which stood at $3.95 per gallon. Wholesale ethanol was unchanged at $2.16. Natural gas prices at the Henry Hub reporting site dipped 23 cents to $2.31 per MMBtu.