CARFAX One-Owner. Clean CARFAX. 2021 GMC Terrain SLT AWD 9-Speed Automatic 1.5L DOHC 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.