I wanted to jump in and give some useful advice on this thread regarding the 5w50 motorcraft.
Ford is obviously going to recommend their own brand. But this is an "intended use" package on this car, and therefore Ford assumes at least one of us will actually do extreme track work and doesnt want the motor seizing up. Currently, if your a worry wort about your warranty, you can only use Motorcraft 5w50 or you can use the Castrol Syntec 5w50. These as far as I know are the only two Ford will recognize as being covered under warranty due to the specific certifications.
However, UOA's have already shown that 10w30 Amsoil, and even Royal Purple are superior, at least on the analysis sheet. Ford's engineers are not stupid, but what their not telling you, is about the quality of their oil. Under street racing conditions or light tracking, the 5w50 Motorcraft is shearing to a light 5w40 at running tempurature. Under extreme conditions, its even shearing down to a heavy 5w30.
By this, I would rather run a quality oil thats ALWAYS a 30w oil with minimal shearing. Amsoil 10w30 is my choice. And the 10w is soley because we live in Texas.
With a quality 30w, your going to have the same if not better protection, and slightly improved fuel mileage. If your worried about warranty, you can use the cheaper Motorcraft. The same engine runs 5w20 in non track pack AND non boss cars. They assume its your daily driver (the base model), not a race car.
Pick the oil for your intended use, and pick a quality one.
Edited for JDMLOL's reading pleasure
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