I don't know if this is something that has been discussed, but I wanted to bring it up in light of the substantial price difference per quart between Mobil 1 and other full synthetic oils. Since Mobil 1 is now $5.29/qt even at Costco, I am considering changing over to either Pensoil Platinum full synthetic or Quaker State full synthetic. Is there really THAT much of a difference between Mobil 1 and these products? I mean, it is almost $2 a quart in my area. I was just curious on what everyone's thoughts are.