http://www.consumerenergycenter.org/...s_premium.html
Octane is defined as a fuel's resistance to knocking. There is no benefit if the octane is higher than what the engine needs. Engine knock occurs when fuel in a combustion chamber ignites before it should. This disrupts the engine's operation. But electronic knock sensors are now common and have nearly eliminated engine disruption.
The American Petroleum Institute says if you find that your car runs fine on a lower grade, there is no sense switching to premium. The Institute recommends following manufacturer's recommendation, but even those manufacturers say that it is more of a suggestion than a command.
Just putting out there what I have found.......My son swears by Premium in his Lexus...I use the middle grade 89, and add octane boost per tank (if more than half gone)....never had a problem in any High Performance car.......but I'm not saying "im right" by any means-