So you want the best motor oil money can buy and as well as the best motor oil known to man? You need Royal Purple. Royal Purple is a super fine synthetic oil that exceeds any synthetic oil on the market.
For your Mustang I recommend that you check the owner's manual and see what kind of oil it takes. Once you know what weight of oil it takes this is what you do next:
Go here and find the nearest dealer for this motor oil
http://www.royalpurple.com/dealers/dealers.html
Once you do that you can find directions to this dealer by going here:
http://www.mapquest.com
They sell for about $4 bucks a quart and since your Mustang is a V6 it will probably take at least 6 bottles of Royal Purple synthethic. Now just take it to a Jiffy Lube and tell them you have your own oil and they will give you a $20 discount and you only pay $29.95.
Tell them you want to completely change the oil on your Mustang and fire it up.