i use Fina because out here in Lubbock the octane ratings are 86, 88, and 91 and Fina is the only station chain that uses 87 for it's regular (like NORMAL) and it's cheaper to buy regular at Fina then it is to buy mid-grade elsewhere.
they just started doing this last summer though, so before that i used Diamond Shamrock because they were usually a couple cent's cheaper than the rest.
as you can see, i'm driven by price
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