Michigan's average gasoline price climbed 12 cents from a week earlier to $4.27 a gallon, according to AAA Michigan, extending increases from both the prior month and last year. The statewide average is 19 cents higher than a month ago and $1.13 above the level a year earlier. Ann Arbor and Jackson recorded the highest prices in the state at $4.33 a gallon, while Marquette in the Upper Peninsula had the lowest at $4.05. At the statewide average, filling a 15-gallon tank costs about $64. In southwest Michigan, St. Joseph County posted the lowest price at $4.10, while Barry County remained the region's most expensive at $4.37.