Hey,
Pretty new here as i just bought my first GP last week. It's a '99 GTX.
The guy I bought it off of (which is also the original owner) ran 87 Octane in it it's entire life until now. I'm aware that the car was designed to use premium fuel, and am wondering what effects being run on 87 for 9 years could have caused? Should I be worried about this? I assume I should start running 91 octane in it?
One more question..Is it harmful to switch back and fourth between grades of fuel for testing purposes (eg fuel mileage).
Any help is much appreciated as I'm super pumped to get some miles on her.
Thanks
