Edit: Now that I have my Cobra I use Mobil1 5W-30 synthetic with Motorcraft FL-820S filter. I got too much valvetrain noise with the above oil that I used on my GT.
Amsoil 5w20 for motor oil, along with their severe duty gear oil and sythetic atf for the tranny fluid. Hasn't ever let me down and the extended drain is awesome! Worth the extra loot, IMHO.