Fran O'Hagan, head of research firm Pied Piper, says Mercedes-Benz has benefited from moving its dealership model from a “museum curator” approach to “being as helpful as they can, turning car shoppers into Mercedes owners.” In the end, it’s often the way a dealer treats customers that can make or break a sale no matter how good the vehicle, O’Hagan emphasizes. Mercedes-Benz leads in the Pied Piper Satisfaction Index, based on reports by mystery shoppers. Infiniti, Lexus, Mini and Toyota round out the top five, and BMW, at sixth, has begun climbing the charts.