Mazda Repair: Regular fuel in a 2008 Mazda CX-7, premium fuel, highway speed

Question
Hello,
The owner's manual on our new '08 CX-7 recommneds premium fuel of 91 octane or higher. The word "recommended" is used, not "required".  Would use of 87 octane damage the engine?  I understand performance may be reduced, but during times of high fuel cost, would we be okay running "regular"?
Thank you!

Answer
In around town, start and stop especially in the summer months I suggest premium or at the least mid grade.

If you commute or are taking a trip and are traveling at highway speed on relatively flat terrain and at or near sea level then low grade is fine the vehicles computer control will adjust to compensate to a degree.  If at anytime knocking on acceleration or rattling is heard then increase to the next highest grade of fuel.