Hey I just got a 2001 gt and am going to be changing the oil in it. I am planing on either using mobil 1 or royal purple. I am thinking about going with the 5w-30 instead of the 5w-20 because its a little thicker. I also heard the only reason the 5w-20 is recomended is because it helps fuel economy. So who uses 5w-20 and who uses 5w-30 in there 4.6's and why?