The average cost of a gallon of unleaded regular gasoline in Massachusetts is up 4 cents in the past week, but it is still a penny below the national ­average.

AAA Southern New England reports this week that self-serve, regular is up to an average of $3.72 per gallon.

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That’s 1 cent below the national average of $3.73. The price in Massachusetts at this time last year was $3.60.

AAA found self-serve regular selling as low as $3.59 per gallon and as high as $3.87.

Prices have risen 31 cents in the past month.