91 octane is crap- filled with 91/100 blend
We have all seen Pencilgeek's dynos which show a 30+ ft-lb improvement around 2-3k and ~35hp around 8200, but the peak figures do not tell you what the actual improvement in driving feel is.
The car runs noticeably smoother and less jerky, especially when cold. It has a lot more low end torque below 3000 RPM in day to day driving.
91 octane CA gas at sea level is crap, the engine has to detune itself a lot to run on it. I remember in Europe during my ED running 98 (equiv 94) the car ran smoother. (That was 4,000 miles ago.) Sure it will run on 91 and not hurt itself but the car truly benefits from 94-95+ MON gas at 12:1 compression.
I recommend Sunoco street fuels GT100 (100 octane). The Torco stuff available around some stations in CA is rumored to not be a fuel safe for long term use in street engines. Subaru WRX/STI tuners have noted that it leaves red (?) buildup on the inside of your motor. I'm no expert but the Sunoco stuff is proven to run clean. I think I'm going to mix some 100 into every tankful, even at $8/gal. Premium is $4.50 where I am, so it's an extra $25-30 per tank. Not that bad IMO but then again my commute is only 3.5 miles.
Last edited by smmmurf; 04-21-2011 at 11:43 AM.