Gas prices continued to retreat this week, with the statewide average falling about a penny and a half to $3.57 per gallon of regular on Thursday, says AAA Arizona.

The national average dropped almost a nickel to $3.59.

Arizona drivers continue to pay higher prices compared with a year ago, but the difference has narrowed to 4.5 cents compared with 18.5 cents at the beginning of July, AAA said.

Tucson and Flagstaff had the lowest and highest state fuel-price averages on Thursday at $3.38 and $3.80 per gallon, respectively.