I have a BRZ and I've been experimenting filling up at the pump, I'm in north cal so 93 octane doesn't exist. So we only have 91, the first week I got the brz back in December i filled up at Costco and would average a rang of 220-230 on the digital cluster. After that I've been filling up at Arco and 76 and would average 230-240. And ever since I switched to Chevron I'm averaging 260-280 I'm just curious why does it fluctuate with different brands? I'm assuming it's the same gas but with their own additives for each station? Also wanted to add on with Costco I did hear a weird rattle everytime I cold start it, so I'm not sure if it's the gas itself but after not using that it went away. What are you guys averaging for your range?