FWIW I've used the 5w-50 from Castrol and liked it. Problem is I think they're going to discontinue it due to the heavy weight when hot. Most of the newer engines are now so close in tolerances which allow smaller, lighter, higher horsepower engines to be built that they need a lower viscosity oil. Hence the reason Ford/Mazda have gone to a 5w-20 for nearly all of their newer "cars". Like my Tribute. I use Amsoil 0w-30 and before that it was the Mobil 1 0w-30. I LOVE Amsoil and am hooked on it for life. The cost is more expensive but the piece of mind is so worth it.
HTH
John
