Word of mouth sells cars. And word of mouth on the Web travels farther and faster. Auto marketers want to fuel Web-based word of mouth by finding and harnessing online brand advocates. But to do so they must recognize that consumers who post user-generated content about vehicles are only half the story. Those who simply view it are the other half. Understanding these groups' differences will give marketers the framework to seek the right insights in social media, and then use it to create two messaging strategies that will set online word of mouth on fire.