You may or may not notice it, but the lower rated gas will hinder your performance and economy a bit. If you Have to run lower grade gas due to your state, look into getting the STP Octane Booster (Orange Bottle) It will help bring the octane rating up a few points.
I use the OB and the Gas Treatment in every tank and it's netted me 2 mpg more avg than other Z's for the entire time I've had the car.
