oil viscosity

My 06 Mustang GT is in the shop getting some work done. I would like to pick up a case of Royal Purple after work but I can't remember what viscosity oil I need. Can anyone here help me out?

Most cars use 5W-30 for the last few years. However, Ford has gone to a 5W-20 for increased fuel mileage. If you are under warranty, stick to Ford's recommendation. If not, I use a synthetic 5W-30 in my '01 Cobra.

Good luck....