Motorists are paying about 31 cents more for a gallon of gas than they were one month ago, AAA Southern New England says.

The not-for-profit auto club's latest Monday price survey had self-serve regular in Massachusetts averaging $3.72 per gallon, up four cents from last week.

Self-serve midgrade is averaging $3.88 per gallon, and self-serve premium is averaging $4.01 per gallon, AAA said in a press release.

Today, Patch's gas price tracker shows the lowest price in Westborough for regular at Gulf, on the Mass Pike westbound, at $3.78 per gallon. Mobil, at 130 Turnpike Road, is charging $3.80 per gallon. Westborough Mobil, at 24 East Main St., is charging $3.84 per gallon.

The lowest prices for midgrade are: Mobil, at 130 Turnpike Road, $3.90; and Gulf, on the Mass Pike westbound, $4.07.

The lowest price for premium is at Shell, 27 East Main St., $4.04.