Multiple gasoline vendors have been overcharging customers on the state Thruway, according to a recently released state audit.

In a written announcement, state Comptroller Thomas DiNapoli said this week that three gas stations have been violating service contracts by charging between 2 cents and 26 cents too much per gallon.

Some Thruway stations have also failed to post gas prices appropriate for the days they were posted, according to the audit.

DiNapoli estimated in his statements that customers overpaid approximately $2,900 between May 1 and Aug. 30, 2008, at Sunoco and Lehigh stations selling Mobil gas in Dewitt, Sloatsburg and New Baltimore.

Under the contract between the state Thruway Authority and the companies, station operators are required to set prices based on those at other gas stations in the region, according to DiNapoli's office. Sunoco and Lehigh are also required by the contract to survey local gas prices every week and adjust their prices with the Thruway Authority's approval, the release stated.

According to the audit, the Thruway Authority approved prices that exceeded limits set in the contracts, and it did not always properly verify the accuracy of the price surveys conducted by Sunoco and Lehigh, DiNapoli's office stated.

“The amounts were small,” DiNapoli said of the price hikes in the statement, “but it can make a big difference to businesses and drivers who are frequent travelers on the Thruway.”

In response to the survey, the Thruway Authority has stated it will launch its own investigation to help improve the pricing process.

There are 27 travel plazas on the Thruway. Stations at Angola, Clarence, Guilderland, Malden and Ulster were also included in the audit.