Mercedes-Benz, GM, Toyota, Chevrolet and Acura are getting the best buzz among automakers from their social media mixes, according the NBCUniversal Integrated Media's Brand Power Index. Mercedes enjoyed a 52% increase among women and 36% among men via a combination of food and music programs as well as the Style Furniture Collection. And Toyota gained ground among men and women with its concert series on NBC's "Today" show and Pandora's streaming-music service.