E-ZPass can get you 30 cents a gallon discounts at some gas stations

BOSTON -- If you use E-ZPass to pay tolls on the highway, you can also use it to buy cheaper gas for a few weeks too.

E-ZPass has partnered with Boston-based PayByCar to offer drivers the chance to save 30 cents a gallon on gas at more than two dozen gas stations in Massachusetts through Labor Day.

PayByCar is a startup company that's created a system that allows drivers to buy gas with their E-ZPass at 27 Alltown Mobil gas stations .

The cost of the gas is not charged to the E-ZPass. When you sign up for PayByCar you create an account with a credit or debit card and then link your account to your E-ZPass transponder. You then use the transponder and your phone to buy the gas. You'll get a text message when you pull into the gas station and if you accept, you don't need to do anything else but pump the gas.

Watch: How PayByCar works

According to AAA , the average price of gas in Massachusetts as of Thursday is $4.44 a gallon.

The promotion with the Massachusetts Department of Transportation is valid through Monday, September 5.