branded (chevron) or generic (costco) gas??

[static808]

kaotic's topic led me to thinking about the brand of gas we all put in our cars. is there any research or information about the quality of brand (shell, chevron, etc...) and non-brand (costco, etc...) gas?? with prices the way they are, i've been putting costco gas for quite some time (might as well since we pay for membership already, and theres one 1.5 miles away). performance and mileage have been exactly the same with what we used before, which is strictly chevron (love that techron). i was thinking of simply using costco gas and throwing in some concentrated techron (or any fuel cleaner) every few months with my gas savings. can i stick with this "cheap" course of action, or should bite the economic bullet and go back to good ol' chevron?? thanks again for any input and advice...!!

--B

ps: all in all, we will save just under 200 bucks a year by going the cosco route, for both of our cars, so its not just a couple of bucks we're debating over...