CARFAX One-Owner. Clean CARFAX. 2020 GMC Terrain SLE AWD 9-Speed Automatic 1.5L DOHC Odometer is 8519 miles below market average! 25/28 City/Highway MPG AWD. The Vachon Auto Group has been in business for over 70 years and has served Old Saybrook, Old Lyme, Niantic, Westbrook, Clinton, and Madison, CT for the past 3 years.