Mercedes leads the luxury car world when it comes to using social media. That's according to social media experts eBench, which surveyed Mercedes, Audi, Aston Martin, BMW, Ferrari, Porsche, Jaguar, Land Rover, Lexus and Lamborghini to see how well they connected with customers. Mercedes has a particular lead in the fastest growing social media outlet, Instagram, which is considered important because, unlike Facebook and Twitter, you can't pay to advertise or promote your products there. Only on YouTube does Mercedes lag behind its key rivals, Audi and BMW.