Years back, in 2004 when I bought my Boxster, I experienced fluctuation on my tachometer when I got gas at Costco (still 91 grade). My service advisor suggested Chevron 91 (all that is available in Cali) and I was wondering what brand of gas do other Porsche owners use? My car runs great with Chevron 91 but I was curious about what other Porsche owners run
