To me, oil is oil, changing it is the important part. I've always run Castol GTX 5W-30 and it's still a beautiful shade at change time, I do it every 4000 km's or 2-3 months as it works out. If you want to run synthetic, nows the time to swap. I am a true follower of product advertising, favorite driver: John Force, sponsored by Castrol and Fram, well sh-t, that's what's on the truck right now. Motorcraft oil is the only other I've used. Where I buy is usually limited to brands, so I haven't really strayed much. Quaker State, Pennzoil, Mobil, Havoline, don't worry, just the mileage matters. Oil filters I say Motorcraft or Fram, whichever end works best for your filter wrench or socket or hand.