I thought BP claims their gasoline would pass the Top Tier standards but since they (BP) view it as mostly a marketing ploy (by GM and other manufactures), they opted to not have it certified or what ever. And doesn't Ford recommend BP? (at least it sez so in wikipedia )
Now just to let you all know, I am a GM kinda guy and use Exxon, a top tier brand but more because it is the easiest station for me to stop at after work.
Besides, I'd never put something recommended by Ford in my GMC!!!