I just purchased a used 2013 5.0 V8 Mustang with the Trac Pack performance option with 13,000 miles. The oil cap on the motor says use 5w20 oil although I was reading on another forum that the 5.0 V8 motor with the Trac Pack was upgraded to use 5w50 oil? The dealership was not much help the service clown behind the desk just looked at me and said "If the oil cap says 5w20 just stick with that" I wanted him to at leased look in his Ford computer to see if there were any updates. Thanks for any advice