Ford Mustang (2005-2014) Owners Manual: Summer tires (if equipped)

Summer tires provide superior performance on wet and dry roads. Summer tires do not have the Mud and Snow (M+S or M/S) tire traction rating on the tire side wall. Since summer tires do not have the same traction performance as All-season or Snow tires, Ford does not recommend using summer tires when temperatures drop to approximately 40°F (5°C) or below (depending on tire wear and environmental conditions) or in snow and ice conditions.

Like any tire, summer tire performance is affected by tire wear and environmental conditions. If you must drive in those conditions, Ford recommends using Mud and Snow (M+S, M/S), All-season or Snow tires.