From what the service manager told me about someone's case
When it comes to oil and warranty, you need the special blend that Ford uses or the full extended synthetic like Mobil 1 has.
Ford uses these formulas to increase MPG numbers and longevity.
Your service manager is spinning a yarn. There is absolutely no truth at all in Ford requiring a certain brand oil for warranty purposes. UNLESS they are providing it under a service plan where they provide the oil for free. Unless they are doing that, it is illegal for them to void the warranty because you don't use the brand they recommend.
As for requiring a synthetic blend, etc. As long as the oil you are using is the correct weight then they cannot void the warranty unless they actually PROVE that the oil failure caused an internal engine failure. A synthetic blend is not going to provide the best mpg. Only a full synthetic will do that.
All that being said. Mobile, RP, AMSOIL, etc are ALL good quality oils. Deciding which one to run depends on your own personal wants and needs according to how you want to manage your maintenance schedules. People who use AMSOIL for extended intervals of up to 25K miles and in some cases more than that on one oil change will see the same results as someone who is running Mobile EP for 10-15K miles except for one difference. The person running the AMSOIL for the extended interval is going to spend less money annually on their maintenance.
Now, I NEVER recommend anyone make the change to AMSOIL, RP, Mobile or any other brand and extend their intervals in blind faith. YES, AMSOIL Guarantee's their oil (when used with their EA filters) for up to 25K miles or one year under NORMAL driving conditions and 15K miles or one year under Severe Duty driving conditions. However, every vehicle, person, driving condition, climate, etc, etc, etc is different and as a result some engines are harder on oil than others. I highly recommend that anyone that wants to extend intervals at all, do so by utilizing used oil analysis to allow a lab to determine your intervals. Doing so will help you head off possible problems, let you know whether the oil is holding up, whether it is full of contaminants, etc. Those customers of mine that use AMSOIL (I also sell RP, Champion and others) and utilize UOA still spend less annually.
I also agree, bobstheoilguy is a great informative website. But there is as much if not more opinion based assumptions there as there are on any other website.
