and read the whole thing before you bite my head off about it, and i am not trying to say that all you out there using 5w-30 and any other weight are wrong just maybe uninformed
No you just posted a link to a old post that stated Ford has deemed "said" engines to be able to run the CAFE/EPA improving 5W20.
Ford only picked 5W20 because it raised their average fleet MPG. This way they could sell more trucks and not have to make them actually run any more efficiently!
It is NOT because it makes the engines last longer. It actually causes a lot more long term wear on the engine to run with a much thinner, less protective oil. Oil viscosity is a trade off between overall operating protection, parasitic drag, and start up flowability. (since most wear occurs at startup!)
Please get your facts straight because this thread is already chalked full with enough blatantly ignorant posts.