00 4.6 motor in 96 tbird, motor has about 20k (got it with 12k), so far ive been using mobile 1 synthetic 5w30 with a motorcraft filter, that was in the winter, yea i drive it daily, in the warmer weather what should i run? is the synthetic really all that its cracked up to be? or am i just waisting my money with it. should i go to a synthetic blend? or a non synthetic?