It maybe Quaker State, not Mobile 1 or Amsoil but I only run a stock 04 GT, non modded.
It was a stretch switching to synthetic instead of running regular 5W30 for a highway runner. The only reason I picked it up and this is going to sound bad is.... because it was on sale. When Mobile one comes down in price from $100 a jug to $99 a jug, maybe ill consider it. Until then.... Quaker State it is!