As sales sputter, are muscle cars the canaries in the industry coal mine? by deeperkins | Aug 22, 2016 | Uncategorized After hitting a five-year peak in 2015, combined sales of the Ford Mustang, Chevrolet Camaro and Dodge Challenger have declined 8.4 percent this year. So is it time to worry about America’s fabled muscle-car troika? Source: Auto Feed