[denverpete]

Jim has some good points. In my previous life I had to inspect bulk fuel terminals. As Jim stated, they don't have separate tanks for each vendor. The only separate tanks are for the different Octane Ratings. Chevron tankers load up right next to Wal-Mart and others. Next to the loading stations is a VERY small shed containing tanks with each vendor's "proprietary" fuel additive. These tanks couldn't have been more than a few hundred gallons each. Compare this to the bulk tanks which are in the millions of gallons range. So, you know there's only a miniscule amount of additive per gallon. I'm not saying that some additives aren't better or more effective than others - but there is absolutely no difference in the base fuel.

As to getting more power from higher octane (or less power from lower octane), I'll defer to Jim on that one. But, I did see an interesting Speed Week last night where they actually took a 997 and dyno'd it with regular and then with premium. They reported a 5hp difference between the two.