Originally Posted by fastdude007
I also tried running 91 octane fuel for a month which did not do anything for the performance. However I do feel the difference between 87 octane and 89 octane. 89 octane fuel seems to get me the best performance and fuel economy for my engine.
Wouldn't the compression ratio of the engine dictate what the fuel octane needs to be? Since CAI, cat-back, and throttle body don't modify the internal workings, the fuel required would stay the same. At least, that's how it seems to me. I'm certainly no mechanic.
As I will be traveling a lot for work and putting on a lot of miles, increasing fuel economy is my main goal. The way I understand it, intake and exhaust mods allow the engine to breathe in and out more thoroughly, and thusly allow for the optimal air/fuel mixture to be achieved at more points across the RPM range. More ponies would of course be nice, but I just want to make sure I'm not sacrificing economy for performance.