I find this kind of interesting and I'd thought I'd let the fellow L owners know... I called SVT today and asked them about going to 5w-30 Mobil 1 on my 2001 and told him that I had heard that this would not be a problem NOR affect the 36/3 warranty. He(can't remember his name, flame me if you want!) shockingly said, "who told you that!" Then went on to say, "SVT does not recommend using synthetics since all our testing done on the Lightning was conducted using conventional oil only." I then asked if Motorcraft conventional oil is what is recommended and he said,"Not just Motorcraft but ANY 5w-20 conventional oil should be the only oil to use." I then asked about the internals of the 2000 Lightning compared to the 2001 and he said, "there is no difference between 2000 and 2001." So I quickly stated "Then 5w-30 would not be a problem or conflict the 36/3 warranty?" From there, he stuttered and seemed to try to gather himself to quickly state, "I recommend you call your service dealer and direct warranty related questions to him."
Well, I was kind of surprised....I was all but sure about 5w-30 Mobil1, now I'm hesitant.

 

Unless the vehicle comes from the factory with synthetic oil, Ford will never say it's ok to use. Too much liability.

 

I just had my dealer do the 3000 mile oil change (they gave it to me free). They used 5W30.

Seems pretty clear that 5W30 should be good (or at least covered under warrenty).

I'm not about to get into the Synthetic/conventional holy war.

Coldie