does it really matter? cause it seems to be a hell of alot cheaper than premium...

 

I ran 89 with no problems, but after the cam change I'll be running premium only. Most recommend it.

 

Only "matters" if you don't mind giving up a bit of HP. But the actual impact will depend on a lot of things, including the altitiude where you live, the ambient air temperature, how hot or cool your engine runs, how much the compression ratio has been boosted by carbon buildup, etc. Put a scanner on it, and watch for knock retard. If you get knock retard, you are losing performance.

 

The previous owner of my '94 Z28 ran 87 octane in it and said it ran fine. Granted I bought it with a bad fuel pump (~132k miles) The engine will retard the timing, and the car won't run as good but it won't really hurt anything.

I personally say just run what it's suppose to run. The fuel economy/performance increase will negate any additional cost. Besides, what is $.20-.30 when your spending $3.00 a gallon?