I was wondering if any one uses costco 91 for their S?

 

I have been, for the price difference and the fact that I was mostly commuting, it was a no brainer. I do use 92 on the weekends though when i can find it. Or I add a couple of gallons of 100 octane Unocal76 racing fuel once in while.

 

I use it as regular as I can, I just throw in an octane boost every once in a while (once a month or so). It seems to work fine.