Thanks all for the suggestion.
I always use premium Octane 91 at Co-op Gas Station for my other cars.
I am thinking to use same for my BRZ, any comment?

Esso and Shell 91 are true 91 octane gasoline with no ethanol added. Co-op will be a lower grade with ethanol added to bring it up to 91. Personally, I would never gas up at Co-op, Superstore, etc. Particularly when you can pay the same or only a few bucks more for the real thing.

For those who think a few bucks is a big deal, they could save a lot more by buying a cheaper car. Using things like lower grade gas (<91 or even 91 when 93/94 ethanol free is available) is like putting Wal-Mart tires on a performance car—why bother getting a performance car in the first place?

Ethanol is a stickier issue, but I'm not paying the same price as gasoline for corn and then getting worse mileage. Engines are built to tolerate up to 10% ethanol, but higher amounts (even 15%) do engine damage (as it warns in the manual), which leads me to deduce that 10% ethanol is tolerated but likely not good or optimal for the engine.

You would lose power and timing with 91 at sea level. It will work fine of course, as California needs to be good on 91.

At 3000 feet 91 is like 93 because of the thinner air. We'll also be slower across the board than our turbo/supercharged friends.

Hmmm, Shell maxes at 91 and is right by the house or... go for 94 at Chevron somewhere else. So from what you're saying, Shell 91 is ok, but Chevron 94 is preferred...

You're at sea level peazs. If you were to use 91 it would be okay. But using 94 would give you top performance.

Just picked up my 10 series FR-S a week and a half ago. Not sure what the dealer put in but I've been filling up with Shell 91 octane and am getting 8.1L/100km. It is sort of out of the way though. Any thoughts on using PetroCanada 91/93 octane?

If your gonna go petro go with 93, wait I think it's 94 actually.
Even though I would never fill up there or anywhere really besides Shell and if I'm desperate I'll use Esso

94 at Chevron I read should be the best bet! I believe this is ethanol free...

Shell 91 for me, I would go to 94 if I had a full exhaust, tune and intake.

what about Petro Canada 91?

I originally thought I should get gas at a more "known" place like a Shell or Petro Canada and i was getting consistent 490km's to a tank, or an average of 8.5L/100km's (as per what my dash said).
Now I get gas whenever I need gas, at whatever gas station I see first......and am getting 490km's to a tank or 8.5L/100km's........all with no noticeable difference in performance.
To each their own, but with Zero difference for me, I am not going out of my way, or spending more for something that gives no difference.
I also have a friend who's Dad works for a major oil/gas company that told me that ALL gas comes from the same storage tanks (in Calgary) and is picked up by different fuel tankers (with different names on them like Shell/Petro etc) and delivered to the pumps. I don't know if this is true, just what he told me, although I do know that there is a lot of competition for gas, and marketing/gimmicks are used all the time to get people to use a specfic company's fuel......again, just my opinion, but I'm sticking with what works for me!

Don't believe everything you read. Chevron has 10% Ethanol (shit). 91 without ethanol is better than 93 or 94 with ethanol. Ethanol is bad, will make your car run worse, your fuel pump chirp, and puts water in tour tank. Stay away from it if you want your car to last. Just my 2 cents.
Pure-Gas website lists all stations in Calgary without Ethanol.

How about Coop gas 91?

Pure Gas website is almost entirely wrong for Calgary. The only ethanol free gas here is Shell 91. I have been running Husky 94 for 63000 kms and my car runs better than on Shell and other 91oct available here. This is based off my own data logs. I tend not to believe everything I read when especially when it's unsupported by any real facts.