Gas prices in Massachusetts are up another four cents since last week, AAA Southern New England said today.

Prices remain 31 cents higher than a month ago, according to the agency's weekly price survey.

The average self-serve prices are: regular, $3.76 per gallon; midgrade, $3.90 and premium, $4.04.

According to Patch's Commute feature, the three lowest prices for regular in Westborough are: $3.66, Westboro Sunoco, 49 Milk St.; $3.81, Mobil, 130 Turnpike Road; and $3.87, Gulf on the Mass Pike.

The three lowest prices for midgrade are: $3.96, Mobil, 130 Turnpike Road; $4.01, Shell, 27 East Main St.; and $4.06, Shell, 128 Turnpike Road.

The three lowest prices for premium are: $4.15, at Shell at 27 East Main St. and Gulf on the Mass Pike; and $4.19, at Shell, 128 Turnpike Road.