Originally Posted by
channelmaniac
On my 03 I can tell a BIG difference in the Butt Dyno and in the Wallet Dyno if I run anything less than premium (91/93 octane depending on state)
It costs more to fill the car up with lower octane as your engine will retard the timing automatically to account for knock and ping. You will feel the performance drop AND you will notice worse gas mileage - enough so that you will spend more money on fuel if you use the cheaper gas.
YMMV, that's just my experience with my 03.
RJ